Errors (#2290)

* add errors.As

convert target err to *Error, return false if err don't match *Error

* update errors.As to (*Error, bool)

* fixing FromError panic issue when err is nil

errors/errors.go

@@ -4,6 +4,7 @@ package errors
 
 import (
 	"encoding/json"
+	"errors"
 	"fmt"
 	"net/http"
 )
@@ -138,9 +139,24 @@ func Equal(err1 error, err2 error) bool {
 
 // FromError try to convert go error to *Error
 func FromError(err error) *Error {
+	if err == nil {
+		return nil
+	}
 	if verr, ok := err.(*Error); ok && verr != nil {
 		return verr
 	}
 
 	return Parse(err.Error())
 }
+
+// As finds the first error in err's chain that matches *Error
+func As(err error) (*Error, bool) {
+	if err == nil {
+		return nil, false
+	}
+	var merr *Error
+	if errors.As(err, &merr) {
+		return merr, true
+	}
+	return nil, false
+}