oh-my-zsh/plugins/go/go.plugin.zsh

# install in /etc/zsh/zshrc or your personal .zshrc

# gc
prefixes=(5 6 8)
for p in $prefixes; do
	compctl -g "*.${p}" ${p}l
	compctl -g "*.go" ${p}g
done

# standard go tools
compctl -g "*.go" gofmt

# gccgo
compctl -g "*.go" gccgo

# go tool
__go_tool_complete() {
  typeset -a commands build_flags
  commands+=(
    'build[compile packages and dependencies]'
    'clean[remove object files]'
    'doc[run godoc on package sources]'
    'fix[run go tool fix on packages]'
    'fmt[run gofmt on package sources]'
    'get[download and install packages and dependencies]'
    'help[display help]'
    'install[compile and install packages and dependencies]'
    'list[list packages]'
    'run[compile and run Go program]'
    'test[test packages]'
    'tool[run specified go tool]'
    'version[print Go version]'
    'vet[run go tool vet on packages]'
  )
  if (( CURRENT == 2 )); then
    # explain go commands
    _values 'go tool commands' ${commands[@]}
    return
  fi
  build_flags=(
    '-a[force reinstallation of packages that are already up-to-date]'
    '-n[print the commands but do not run them]'
    "-p[number of parallel builds]:number"
    '-x[print the commands]'
    "-work[print temporary directory name and keep it]"
    "-gcflags[flags for 5g/6g/8g]:flags"
    "-ldflags[flags for 5l/6l/8l]:flags"
    "-gccgoflags[flags for gccgo]:flags"
  )
  __go_list() {
      local expl importpaths
      declare -a importpaths
      importpaths=($(go list ${words[$CURRENT]}... 2>/dev/null))
      _wanted importpaths expl 'import paths' compadd "$@" - "${importpaths[@]}"
  }
  case ${words[2]} in
  clean|doc)
      _arguments -s -w : '*:importpaths:__go_list'
      ;;
  fix|fmt|list|vet)
      _alternative ':importpaths:__go_list' ':files:_path_files -g "*.go"'
      ;;
  install)
      _arguments -s -w : ${build_flags[@]} \
        "-v[show package names]" \
	'*:importpaths:__go_list'
      ;;
  get)
      _arguments -s -w : \
        ${build_flags[@]}
      ;;
  build)
      _arguments -s -w : \
        ${build_flags[@]} \
        "-v[show package names]" \
        "-o[output file]:file:_files" \
        "*:args:{ _alternative ':importpaths:__go_list' ':files:_path_files -g \"*.go\"' }"
      ;;
  test)
      _arguments -s -w : \
        ${build_flags[@]} \
        "-c[do not run, compile the test binary]" \
        "-i[do not run, install dependencies]" \
        "-v[print test output]" \
        "-x[print the commands]" \
        "-short[use short mode]" \
        "-parallel[number of parallel tests]:number" \
        "-cpu[values of GOMAXPROCS to use]:number list" \
        "-run[run tests and examples matching regexp]:regexp" \
        "-bench[run benchmarks matching regexp]:regexp" \
        "-benchtime[run each benchmark during n seconds]:duration" \
        "-timeout[kill test after that duration]:duration" \
        "-cpuprofile[write CPU profile to file]:file:_files" \
        "-memprofile[write heap profile to file]:file:_files" \
        "-memprofilerate[set heap profiling rate]:number" \
        "*:args:{ _alternative ':importpaths:__go_list' ':files:_path_files -g \"*.go\"' }"
      ;;
  help)
      _values "${commands[@]}" \
        'gopath[GOPATH environment variable]' \
        'importpath[description of import paths]' \
        'remote[remote import path syntax]' \
        'testflag[description of testing flags]' \
        'testfunc[description of testing functions]'
      ;;
  run)
      _arguments -s -w : \
          ${build_flags[@]} \
          '*:file:_path_files -g "*.go"'
      ;;
  tool)
      if (( CURRENT == 3 )); then
          _values "go tool" $(go tool)
          return
      fi
      case ${words[3]} in
      [568]g)
          _arguments -s -w : \
              '-I[search for packages in DIR]:includes:_path_files -/' \
              '-L[show full path in file:line prints]' \
              '-S[print the assembly language]' \
              '-V[print the compiler version]' \
              '-e[no limit on number of errors printed]' \
              '-h[panic on an error]' \
              '-l[disable inlining]' \
              '-m[print optimization decisions]' \
              '-o[file specify output file]:file' \
              '-p[assumed import path for this code]:importpath' \
              '-u[disable package unsafe]' \
              "*:file:_files -g '*.go'"
          ;;
      [568]l)
          local O=${words[3]%l}
          _arguments -s -w : \
              '-o[file specify output file]:file' \
              '-L[search for packages in DIR]:includes:_path_files -/' \
              "*:file:_files -g '*.[ao$O]'"
          ;;
      dist)
          _values "dist tool" banner bootstrap clean env install version
          ;;
      *)
          # use files by default
          _files
          ;;
      esac
      ;;
  esac
}

compdef __go_tool_complete go