go help list

usage: go list [-f format] [-json] [-m] [list flags] [build flags] [packages]

List lists the named packages, one per line.

The most commonly-used flags are -f and -json, which control the form of the output printed for each package. Other list flags, documented below, control more specific details.

The default output shows the package import path:

1
2
3
4

bytes
encoding/json
github.com/gorilla/mux
golang.org/x/net/html

The -f flag specifies an alternate format for the list, using the syntax of package template. The default output is equivalent to -f ‘{{.ImportPath}}’. The struct being passed to the template is:

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69

type Package struct {
    Dir            string   // directory containing package sources
    ImportPath     string   // import path of package in dir
    ImportComment  string   // path in import comment on package statement
    Name           string   // package name
    Doc            string   // package documentation string
    Target         string   // install path
    Shlib          string   // the shared library that contains this package (only set when -linkshared)
    Goroot         bool     // is this package in the Go root?
    Standard       bool     // is this package part of the standard Go library?
    Stale          bool     // would 'go install' do anything for this package?
    StaleReason    string   // explanation for Stale==true
    Root           string   // Go root or Go path dir containing this package
    ConflictDir    string   // this directory shadows Dir in $GOPATH
    BinaryOnly     bool     // binary-only package (no longer supported)
    ForTest        string   // package is only for use in named test
    Export         string   // file containing export data (when using -export)
    BuildID        string   // build ID of the compiled package (when using -export)
    Module         *Module  // info about package's containing module, if any (can be nil)
    Match          []string // command-line patterns matching this package
    DepOnly        bool     // package is only a dependency, not explicitly listed
    DefaultGODEBUG string  // default GODEBUG setting, for main packages

    // Source files
    GoFiles           []string   // .go source files (excluding CgoFiles, TestGoFiles, XTestGoFiles)
    CgoFiles          []string   // .go source files that import "C"
    CompiledGoFiles   []string   // .go files presented to compiler (when using -compiled)
    IgnoredGoFiles    []string   // .go source files ignored due to build constraints
    IgnoredOtherFiles []string // non-.go source files ignored due to build constraints
    CFiles            []string   // .c source files
    CXXFiles          []string   // .cc, .cxx and .cpp source files
    MFiles            []string   // .m source files
    HFiles            []string   // .h, .hh, .hpp and .hxx source files
    FFiles            []string   // .f, .F, .for and .f90 Fortran source files
    SFiles            []string   // .s source files
    SwigFiles         []string   // .swig files
    SwigCXXFiles      []string   // .swigcxx files
    SysoFiles         []string   // .syso object files to add to archive
    TestGoFiles       []string   // _test.go files in package
    XTestGoFiles      []string   // _test.go files outside package

    // Embedded files
    EmbedPatterns      []string // //go:embed patterns
    EmbedFiles         []string // files matched by EmbedPatterns
    TestEmbedPatterns  []string // //go:embed patterns in TestGoFiles
    TestEmbedFiles     []string // files matched by TestEmbedPatterns
    XTestEmbedPatterns []string // //go:embed patterns in XTestGoFiles
    XTestEmbedFiles    []string // files matched by XTestEmbedPatterns

    // Cgo directives
    CgoCFLAGS    []string // cgo: flags for C compiler
    CgoCPPFLAGS  []string // cgo: flags for C preprocessor
    CgoCXXFLAGS  []string // cgo: flags for C++ compiler
    CgoFFLAGS    []string // cgo: flags for Fortran compiler
    CgoLDFLAGS   []string // cgo: flags for linker
    CgoPkgConfig []string // cgo: pkg-config names

    // Dependency information
    Imports      []string          // import paths used by this package
    ImportMap    map[string]string // map from source import to ImportPath (identity entries omitted)
    Deps         []string          // all (recursively) imported dependencies
    TestImports  []string          // imports from TestGoFiles
    XTestImports []string          // imports from XTestGoFiles

    // Error information
    Incomplete bool            // this package or a dependency has an error
    Error      *PackageError   // error loading package
    DepsErrors []*PackageError // errors loading dependencies
}

Packages stored in vendor directories report an ImportPath that includes the path to the vendor directory (for example, “d/vendor/p” instead of “p”), so that the ImportPath uniquely identifies a given copy of a package. The Imports, Deps, TestImports, and XTestImports lists also contain these expanded import paths. See golang.org/s/go15vendor for more about vendoring.

The error information, if any, is

1
2
3
4
5

type PackageError struct {
    ImportStack   []string // shortest path from package named on command line to this one
    Pos           string   // position of error (if present, file:line:col)
    Err           string   // the error itself
}

The module information is a Module struct, defined in the discussion of list -m below.

The template function “join” calls strings.Join.

The template function “context” returns the build context, defined as:

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13

type Context struct {
    GOARCH        string   // target architecture
    GOOS          string   // target operating system
    GOROOT        string   // Go root
    GOPATH        string   // Go path
    CgoEnabled    bool     // whether cgo can be used
    UseAllFiles   bool     // use files regardless of //go:build lines, file names
    Compiler      string   // compiler to assume when computing target paths
    BuildTags     []string // build constraints to match in //go:build lines
    ToolTags      []string // toolchain-specific build constraints
    ReleaseTags   []string // releases the current release is compatible with
    InstallSuffix string   // suffix to use in the name of the install dir
}

For more information about the meaning of these fields see the documentation for the go/build package’s Context type.

The -json flag causes the package data to be printed in JSON format instead of using the template format. The JSON flag can optionally be provided with a set of comma-separated required field names to be output. If so, those required fields will always appear in JSON output, but others may be omitted to save work in computing the JSON struct.

The -compiled flag causes list to set CompiledGoFiles to the Go source files presented to the compiler. Typically this means that it repeats the files listed in GoFiles and then also adds the Go code generated by processing CgoFiles and SwigFiles. The Imports list contains the union of all imports from both GoFiles and CompiledGoFiles.

The -deps flag causes list to iterate over not just the named packages but also all their dependencies. It visits them in a depth-first post-order traversal, so that a package is listed only after all its dependencies. Packages not explicitly listed on the command line will have the DepOnly field set to true.

The -e flag changes the handling of erroneous packages, those that cannot be found or are malformed. By default, the list command prints an error to standard error for each erroneous package and omits the packages from consideration during the usual printing. With the -e flag, the list command never prints errors to standard error and instead processes the erroneous packages with the usual printing. Erroneous packages will have a non-empty ImportPath and a non-nil Error field; other information may or may not be missing (zeroed).

The -export flag causes list to set the Export field to the name of a file containing up-to-date export information for the given package, and the BuildID field to the build ID of the compiled package.

The -find flag causes list to identify the named packages but not resolve their dependencies: the Imports and Deps lists will be empty. With the -find flag, the -deps, -test and -export commands cannot be used.

The -test flag causes list to report not only the named packages but also their test binaries (for packages with tests), to convey to source code analysis tools exactly how test binaries are constructed.

The reported import path for a test binary is the import path of the package followed by a “.test” suffix, as in “math/rand.test”.

When building a test, it is sometimes necessary to rebuild certain dependencies specially for that test (most commonly the tested package itself). The reported import path of a package recompiled for a particular test binary is followed by a space and the name of the test binary in brackets, as in “math/rand [math/rand.test]” or “regexp [sort.test]”. The ForTest field is also set to the name of the package being tested (“math/rand” or “sort” in the previous examples).

The Dir, Target, Shlib, Root, ConflictDir, and Export file paths are all absolute paths.

By default, the lists GoFiles, CgoFiles, and so on hold names of files in Dir (that is, paths relative to Dir, not absolute paths).

The generated files added when using the -compiled and -test flags are absolute paths referring to cached copies of generated Go source files. Although they are Go source files, the paths may not end in “.go”.

The -m flag causes list to list modules instead of packages.

When listing modules, the -f flag still specifies a format template applied to a Go struct, but now a Module struct:

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23

type Module struct {
    Path       string        // module path
    Query      string        // version query corresponding to this version
    Version    string        // module version
    Versions   []string      // available module versions
    Replace    *Module       // replaced by this module
    Time       *time.Time    // time version was created
    Update     *Module       // available update (with -u)
    Main       bool          // is this the main module?
    Indirect   bool          // module is only indirectly needed by main module
    Dir        string        // directory holding local copy of files, if any
    GoMod      string        // path to go.mod file describing module, if any
    GoVersion  string        // go version used in module
    Retracted  []string      // retraction information, if any (with -retracted or -u)
    Deprecated string        // deprecation message, if any (with -u)
    Error      *ModuleError  // error loading module
    Origin     any           // provenance of module
    Reuse      bool          // reuse of old module info is safe
}

type ModuleError struct {
    Err string // the error itself
}

The file GoMod refers to may be outside the module directory if the module is in the module cache or if the -modfile flag is used.

The default output is to print the module path and then information about the version and replacement if any. For example, ‘go list -m all’ might print:

1
2
3

my/main/module
golang.org/x/text v0.3.0 => /tmp/text
rsc.io/pdf v0.1.1

The Module struct has a String method that formats this line of output, so that the default format is equivalent to -f ‘{{.String}}’.

Note that when a module has been replaced, its Replace field describes the replacement module, and its Dir field is set to the replacement’s source code, if present. (That is, if Replace is non-nil, then Dir is set to Replace.Dir, with no access to the replaced source code.)

The -u flag adds information about available upgrades. When the latest version of a given module is newer than the current one, list -u sets the Module’s Update field to information about the newer module. list -u will also set the module’s Retracted field if the current version is retracted.

The Module’s String method indicates an available upgrade by formatting the newer version in brackets after the current version. If a version is retracted, the string “(retracted)” will follow it. For example, ‘go list -m -u all’ might print:

1
2
3

my/main/module
golang.org/x/text v0.3.0 [v0.4.0] => /tmp/text
rsc.io/pdf v0.1.1 (retracted) [v0.1.2]

(For tools, ‘go list -m -u -json all’ may be more convenient to parse.)

The -versions flag causes list to set the Module’s Versions field to a list of all known versions of that module, ordered according to semantic versioning, earliest to latest. The flag also changes the default output format to display the module path followed by the space-separated version list.

The -retracted flag causes list to report information about retracted module versions. When -retracted is used with -f or -json, the Retracted field will be set to a string explaining why the version was retracted. The string is taken from comments on the retract directive in the module’s go.mod file. When -retracted is used with -versions, retracted versions are listed together with unretracted versions. The -retracted flag may be used with or without -m.

The arguments to list -m are interpreted as a list of modules, not packages. The main module is the module containing the current directory. The active modules are the main module and its dependencies. With no arguments, list -m shows the main module. With arguments, list -m shows the modules specified by the arguments. Any of the active modules can be specified by its module path.

The special pattern “all” specifies all the active modules, first the main module and then dependencies sorted by module path.

A pattern containing “…” specifies the active modules whose module paths match the pattern.

A query of the form path@version specifies the result of that query, which is not limited to active modules.

See ‘go help modules’ for more about module queries.

The template function “module” takes a single string argument that must be a module path or query and returns the specified module as a Module struct. If an error occurs, the result will be a Module struct with a non-nil Error field.

When using -m, the -reuse=old.json flag accepts the name of file containing the JSON output of a previous ‘go list -m -json’ invocation with the same set of modifier flags (such as -u, -retracted, and -versions). The go command may use this file to determine that a module is unchanged since the previous invocation and avoid redownloading information about it.

Modules that are not redownloaded will be marked in the new output by setting the Reuse field to true. Normally the module cache provides this kind of reuse automatically; the -reuse flag can be useful on systems that do not preserve the module cache.

For more about build flags, see ‘go help build’.

For more about specifying packages, see ‘go help packages’.

For more about modules, see https://golang.org/ref/mod.