runctx: refactoring

- NotifySignals is renamed to DefaultNotifySignals
- Hard coded signals are removed
- New struct Group provides better DSL
- Duplicated code is removed

.golangci.yml

@@ -112,6 +112,10 @@ issues:
         - gochecknoglobals
       source: "(nil)"
 
+    - linters:
+        - gochecknoglobals
+      source: "Default"
+
     - linters:
         - gocritic
       source: "// output:"

cmd/forwarder/httpbin/httpbin.go

@@ -37,7 +37,7 @@ func (c *command) RunE(cmd *cobra.Command, args []string) error {
 		return err
 	}
 
-	return runctx.Funcs{s.Run, a.Run}.Run()
+	return runctx.NewGroup(s.Run, a.Run).Run()
 }
 
 func Command() (cmd *cobra.Command) {

cmd/forwarder/pac/server/server.go

@@ -51,7 +51,7 @@ func (c *command) RunE(cmd *cobra.Command, args []string) error {
 		return err
 	}
 
-	return runctx.Run(s.Run)
+	return runctx.NewGroup(s.Run).Run()
 }
 
 func validatePACScript(script string) error {

cmd/forwarder/run/run.go

@@ -105,20 +105,20 @@ func (c *command) RunE(cmd *cobra.Command, args []string) error {
 		c.httpProxyConfig.ResponseModifiers = append(c.httpProxyConfig.ResponseModifiers, header.Headers(c.responseHeaders))
 	}
 
-	var f runctx.Funcs
+	var g runctx.Group
 	p, err := forwarder.NewHTTPProxy(c.httpProxyConfig, pr, cm, rt, logger.Named("proxy"))
 	if err != nil {
 		return err
 	}
-	f = append(f, p.Run)
+	g.Add(p.Run)
 
 	if c.apiServerConfig.Addr != "" {
 		h := forwarder.NewAPIHandler(c.promReg, p.Ready, config, script)
 		a, err := forwarder.NewHTTPServer(c.apiServerConfig, h, logger.Named("api"))
 		if err != nil {
 			return err
 		}
-		f = append(f, a.Run)
+		g.Add(a.Run)
 	}
 
 	if c.goleak {
@@ -129,7 +129,7 @@ func (c *command) RunE(cmd *cobra.Command, args []string) error {
 		}()
 	}
 
-	return f.Run()
+	return g.Run()
 }
 
 func Command() (cmd *cobra.Command) {

runctx/runctx.go

@@ -15,33 +15,54 @@ import (
 	"golang.org/x/sync/errgroup"
 )
 
-// NotifySignals specifies signals that would cause the context to be canceled.
-var NotifySignals = []os.Signal{syscall.SIGINT, syscall.SIGTERM, syscall.SIGQUIT} //nolint:gochecknoglobals // This is only useful in main packages.
+// DefaultNotifySignals specifies signals that would cause the context to be canceled.
+var DefaultNotifySignals = []os.Signal{
+	syscall.SIGINT,
+	syscall.SIGTERM,
+	syscall.SIGQUIT,
+}
 
-// Funcs is a list of functions that can be executed in parallel.
-type Funcs []func(ctx context.Context) error
+// Group is a collection of functions that would be run concurrently.
+// The context passed to each function is canceled when any of the signals in NotifySignals is received.
+type Group struct {
+	NotifySignals []os.Signal
+	funcs         []func(ctx context.Context) error
+}
 
-// Run executes all funcs in parallel, and returns the first error.
-// Function context is canceled when the process receives a signal from NotifySignals.
-func (f Funcs) Run() error {
-	ctx := context.Background()
-	ctx, unregisterSignals := signal.NotifyContext(ctx, syscall.SIGINT, syscall.SIGTERM)
-	eg, ctx := errgroup.WithContext(ctx)
+func NewGroup(fn ...func(ctx context.Context) error) *Group {
+	return &Group{
+		funcs: fn,
+	}
+}
+
+func (g *Group) Add(fn func(ctx context.Context) error) {
+	g.funcs = append(g.funcs, fn)
+}
+
+func (g *Group) Run() error {
+	return g.RunContext(context.Background())
+}
+
+func (g *Group) RunContext(ctx context.Context) error {
+	sigs := g.NotifySignals
+	if len(sigs) == 0 {
+		sigs = DefaultNotifySignals
+	}
+	ctx, unregisterSignals := signal.NotifyContext(ctx, sigs...)
+
+	var eg *errgroup.Group
+	eg, ctx = errgroup.WithContext(ctx)
 
 	eg.Go(func() error {
 		<-ctx.Done()
 		unregisterSignals()
 		return nil
 	})
 
-	for _, fn := range f {
+	for _, fn := range g.funcs {
 		fn := fn
 		eg.Go(func() error { return fn(ctx) })
 	}
 
 	return eg.Wait()
 }
-
-func Run(fn func(ctx context.Context) error) error {
-	return Funcs{fn}.Run()
-}