Fix double task execution with quiet runner option (#132)

When the `WithRunnerQuiet` option [1] of the `golang` runner [3] or
`WithQuiet` option [2] of the `gotool` runner [4] was set to `true`,
the task passed to their `Run` method [5] was running twice. This was
caused by a missing return statement when the execution finished with a
`error` of value `nil` [^1] [^2].

To fix this bug both code blocks are now returning early with `nil`
instead of keep going on in the code flow.

[1]: https://pkg.go.dev/github.com/svengreb/wand@v0.8.0/pkg/task/golang#WithRunnerQuiet
[2]: https://pkg.go.dev/github.com/svengreb/wand@v0.8.0/pkg/task/gotool#WithQuiet
[3]: https://pkg.go.dev/github.com/svengreb/wand@v0.8.0/pkg/task/golang#Runner
[4]: https://pkg.go.dev/github.com/svengreb/wand@v0.8.0/pkg/task/gotool#Runner
[5]: https://pkg.go.dev/github.com/svengreb/wand/pkg/task@v0.8.0#Runner.Run

[^1]: https://github.com/svengreb/wand/blob/v0.8.0/pkg/task/golang/golang.go#L43-L50
[^2]: https://github.com/svengreb/wand/blob/v0.8.0/pkg/task/gotool/gotool.go#L218-L225

GH-131

pkg/task/golang/golang.go

@@ -47,14 +47,14 @@ func (r *Runner) Run(t task.Task) error {
 				Kind: task.ErrRun,
 			}
 		}
+		return nil
 	}
 	if err := sh.RunWithV(r.opts.Env, r.opts.Exec, tExec.BuildParams()...); err != nil {
 		return &task.ErrRunner{
 			Err:  fmt.Errorf("run task %q: %w", t.Name(), err),
 			Kind: task.ErrRun,
 		}
 	}
-
 	return nil
 }
 

pkg/task/gotool/gotool.go

@@ -222,6 +222,7 @@ func (r *Runner) Run(t task.Task) error {
 				Kind: task.ErrRun,
 			}
 		}
+		return nil
 	}
 	if err := sh.RunWithV(r.opts.Env, execPath, tGM.BuildParams()...); err != nil {
 		return &task.ErrRunner{