go getしたモジュールを削除する

$ go help clean
usage: go clean [clean flags] [build flags] [packages]

Clean removes object files from package source directories.
The go command builds most objects in a temporary directory,
    so go clean is mainly concerned with object files left by other
    tools or by manual invocations of go build.

    If a package argument is given or the -i or -r flag is set,
    clean removes the following files from each of the
    source directories corresponding to the import paths:

    _obj/            old object directory, left from Makefiles
    _test/           old test directory, left from Makefiles
    _testmain.go     old gotest file, left from Makefiles
    test.out         old test log, left from Makefiles
    build.out        old test log, left from Makefiles
    *.[568ao]        object files, left from Makefiles

    DIR(.exe)        from go build
    DIR.test(.exe)   from go test -c
    MAINFILE(.exe)   from go build MAINFILE.go
    *.so             from SWIG

    In the list, DIR represents the final path element of the
    directory, and MAINFILE is the base name of any Go source
    file in the directory that is not included when building
    the package.

    The -i flag causes clean to remove the corresponding installed
    archive or binary (what 'go install' would create).

    The -n flag causes clean to print the remove commands it would execute,
    but not run them.

    The -r flag causes clean to be applied recursively to all the
    dependencies of the packages named by the import paths.

    The -x flag causes clean to print remove commands as it executes them.

    The -cache flag causes clean to remove the entire go build cache.

    The -testcache flag causes clean to expire all test results in the
    go build cache.

    The -modcache flag causes clean to remove the entire module
    download cache, including unpacked source code of versioned
    dependencies.

    For more about build flags, see 'go help build'.

    For more about specifying packages, see 'go help packages'.

go clean -i -n github.com/sample_user/sample

go clean -i github.com/sample_user/sample

rm -rf $GOPATH/src/github.com/sample_user/sample