What causes "too many arguments to goroutine" in go-delve/delve?

Use bare 'goroutine' in on-breakpoint actions: 'on 1 goroutine'

too many arguments to goroutine

Error message

too many arguments to goroutine

What it means

The 'goroutine' command accepts at most one space-separated argument; this error is returned when extra arguments are given, both in the normal path and specifically when used as a breakpoint 'on' action (where only bare 'goroutine' is allowed).

Source

Thrown at pkg/terminal/command.go:977

	if gslen > 0 {
		fmt.Fprintf(t.stdout, "[%d goroutines]\n", gslen)
	}
	return nil
}

func selectedGID(state *api.DebuggerState) int64 {
	if state.SelectedGoroutine == nil {
		return 0
	}
	return state.SelectedGoroutine.ID
}

func (c *Commands) goroutine(t *Term, ctx callContext, argstr string) error {
	args := config.Split2PartsBySpace(argstr)

	if ctx.Prefix == onPrefix {
		if len(args) != 1 || args[0] != "" {
			return errors.New("too many arguments to goroutine")
		}
		ctx.Breakpoint.Goroutine = true
		return nil
	}

	if len(args) == 1 {
		if args[0] == "" {
			return printscope(t)
		}
		gid, err := strconv.ParseInt(argstr, 10, 64)
		if err != nil {
			return err
		}

		oldState, err := t.client.GetState()
		if err != nil {
			return err
		}

View on GitHub (pinned to a23773e6c3)

Solutions

Use bare 'goroutine' in on-breakpoint actions: 'on 1 goroutine'
At the prompt use the form 'goroutine <id> <command>', keeping a single ID argument
Drop extra arguments; run the additional command separately after switching

Example fix

// before
(dlv) on 1 goroutine stack
// after
(dlv) on 1 goroutine

Defensive patterns

Strategy: validation

Validate before calling

// Accept only a single argument for goroutine
args := strings.Fields(argstr)
if len(args) > 1 || (onBreakpointAction && len(args) != 0) {
    return errors.New("usage: goroutine [<id> [<command>]]; on-action requires bare 'goroutine'")
}

Try / catch

err := cmds.Goroutine(term, ctx, argstr)
if err != nil && strings.Contains(err.Error(), "too many arguments to goroutine") {
    fmt.Fprintln(os.Stderr, "use: 'goroutine <id> <cmd>' or bare 'goroutine' in on-actions")
}

Prevention

In on-breakpoint actions use bare 'goroutine' with no arguments
Only pass one ID plus optionally one command at the prompt
Run extra commands separately after switching goroutine

When it happens

Trigger: 'on <bp> goroutine <extra>' with any non-empty argument (only bare 'goroutine' is valid as an on-breakpoint action), or 'goroutine 3 extra' at the prompt.

Common situations: Adding flags or a command after 'goroutine' in breakpoint on-actions; passing multiple tokens expecting them to be chained.

Related errors

AI-assisted analysis of go-delve/delve@a23773e6c3 (2026-08-31). Data as JSON: /api/errors/941e950d4c66fd48. Report an issue: GitHub.