Move some helper functions into dockertestutil package

Signed-off-by: Kristoffer Dalby <kristoffer@tailscale.com>

integration/dockertestutil/execute.go

@@ -0,0 +1,94 @@
+package dockertestutil
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"time"
+
+	"github.com/ory/dockertest/v3"
+)
+
+const dockerExecuteTimeout = time.Second * 10
+
+var (
+	ErrDockertestCommandFailed  = errors.New("dockertest command failed")
+	ErrDockertestCommandTimeout = errors.New("dockertest command timed out")
+)
+
+type ExecuteCommandConfig struct {
+	timeout time.Duration
+}
+
+type ExecuteCommandOption func(*ExecuteCommandConfig) error
+
+func ExecuteCommandTimeout(timeout time.Duration) ExecuteCommandOption {
+	return ExecuteCommandOption(func(conf *ExecuteCommandConfig) error {
+		conf.timeout = timeout
+
+		return nil
+	})
+}
+
+func ExecuteCommand(
+	resource *dockertest.Resource,
+	cmd []string,
+	env []string,
+	options ...ExecuteCommandOption,
+) (string, string, error) {
+	var stdout bytes.Buffer
+	var stderr bytes.Buffer
+
+	execConfig := ExecuteCommandConfig{
+		timeout: dockerExecuteTimeout,
+	}
+
+	for _, opt := range options {
+		if err := opt(&execConfig); err != nil {
+			return "", "", fmt.Errorf("execute-command/options: %w", err)
+		}
+	}
+
+	type result struct {
+		exitCode int
+		err      error
+	}
+
+	resultChan := make(chan result, 1)
+
+	// Run your long running function in it's own goroutine and pass back it's
+	// response into our channel.
+	go func() {
+		exitCode, err := resource.Exec(
+			cmd,
+			dockertest.ExecOptions{
+				Env:    append(env, "HEADSCALE_LOG_LEVEL=disabled"),
+				StdOut: &stdout,
+				StdErr: &stderr,
+			},
+		)
+		resultChan <- result{exitCode, err}
+	}()
+
+	// Listen on our channel AND a timeout channel - which ever happens first.
+	select {
+	case res := <-resultChan:
+		if res.err != nil {
+			return stdout.String(), stderr.String(), res.err
+		}
+
+		if res.exitCode != 0 {
+			// Uncomment for debugging
+			// log.Println("Command: ", cmd)
+			// log.Println("stdout: ", stdout.String())
+			// log.Println("stderr: ", stderr.String())
+
+			return stdout.String(), stderr.String(), ErrDockertestCommandFailed
+		}
+
+		return stdout.String(), stderr.String(), nil
+	case <-time.After(execConfig.timeout):
+
+		return stdout.String(), stderr.String(), ErrDockertestCommandTimeout
+	}
+}