golang/go · error

cannot parse output of GOAUTH command %s: %v

Error message

cannot parse output of GOAUTH command %s: %v

What it means

Emitted from runAuthCommand when the custom GOAUTH command ran successfully (exit 0) but parseUserAuth rejected its stdout. parseUserAuth expects a repeating structure of: one or more absolute URL lines, a blank line, one or more `Name: value` header lines, a blank line (see `go help goauth`). Empty output is allowed and yields no credentials.

Source

Thrown at src/cmd/go/internal/auth/userauth.go:43

	}
	cmd, err := buildCommand(command)
	if err != nil {
		return nil, err
	}
	if url != "" {
		cmd.Args = append(cmd.Args, url)
	}
	cmd.Stderr = new(strings.Builder)
	if res != nil && writeResponseToStdin(cmd, res) != nil {
		return nil, fmt.Errorf("could not run command %s: %v\n%s", command, err, cmd.Stderr)
	}
	out, err := cmd.Output()
	if err != nil {
		return nil, fmt.Errorf("could not run command %s: %v\n%s", command, err, cmd.Stderr)
	}
	credentials, err := parseUserAuth(string(out))
	if err != nil {
		return nil, fmt.Errorf("cannot parse output of GOAUTH command %s: %v", command, err)
	}
	return credentials, nil
}

// parseUserAuth parses the output from a GOAUTH command and
// returns a mapping of prefix → http.Header without the leading "https://"
// or an error if the data does not follow the expected format.
// Returns a nil error and an empty map if the data is empty.
// See the expected format in 'go help goauth'.
func parseUserAuth(data string) (map[string]http.Header, error) {
	credentials := make(map[string]http.Header)
	for data != "" {
		var line string
		var ok bool
		var urls []string
		// Parse URLS first.
		for {
			line, data, ok = strings.Cut(data, "\n")

View on GitHub (pinned to b6b368adc5)

Solutions

1. Read `go help goauth` and emit exactly: URL line(s), blank line, `Name: value` header line(s), blank line.
2. Send any diagnostic/log output to stderr, not stdout.
3. Use LF (\n) line endings, not CRLF.
4. Return empty output (no credentials) rather than malformed text when there is nothing to provide.

// Lint GOAUTH command output against the documented format before use.
func validateAuthOutput(s string) error {
    _, err := parseUserAuth(s) // reuse the parser in a test
    return err
}

When it happens

Trigger: The command prints non-empty output that does not follow the URLs-blank-headers-blank format: an unparseable URL, a header line missing `: `, a missing terminating blank line, or a totally different shape (JSON, free text).

Common situations: Command prints a login banner, debug text, or JSON to stdout instead of the documented format; CRLF line endings; missing trailing blank line; header without a space after the colon.

Related errors

• invalid format: missing empty line after URLs
• invalid format: missing empty line after headers
• could not parse URL %s: %v
• invalid format: invalid header line
• 'git credential fill' failed for url=%s, could not parse url

AI-assisted analysis of golang/go@b6b368adc5 (2026-08-12). Data as JSON: /api/errors/5144b9434608781c. Report an issue: GitHub.