feat(docker): allow specifying docker network, handle error when no network available

internal/docker/errors.go

@@ -0,0 +1,34 @@
+package docker
+
+import (
+	"encoding/json"
+
+	"github.com/yusing/go-proxy/internal/gperr"
+)
+
+type containerError struct {
+	errs *gperr.Builder
+}
+
+func (e *containerError) Add(err error) {
+	if e.errs == nil {
+		e.errs = gperr.NewBuilder()
+	}
+	e.errs.Add(err)
+}
+
+func (e *containerError) Error() string {
+	if e.errs == nil {
+		return "<niL>"
+	}
+	return e.errs.String()
+}
+
+func (e *containerError) Unwrap() error {
+	return e.errs.Error()
+}
+
+func (e *containerError) MarshalJSON() ([]byte, error) {
+	err := e.errs.Error().(interface{ Plain() []byte })
+	return json.Marshal(string(err.Plain()))
+}