remove support to join to older go version

format_test.go

@@ -22,16 +22,22 @@ func TestErrorFormatter(t *testing.T) {
 			detailed{},
 		}
 		nonascii = &wrapped{"café", nil}
-		newline  = &wrapped{"msg with\nnewline",
-			&wrapped{"and another\none", nil}}
+		newline  = &wrapped{
+			"msg with\nnewline",
+			&wrapped{"and another\none", nil},
+		}
 		fallback  = &wrapped{"fallback", os.ErrNotExist}
 		oldAndNew = &wrapped{"new style", formatError("old style")}
 		framed    = &withFrameAndMore{
 			frame: errors.Caller(0),
 		}
-		opaque = &wrapped{"outer",
-			errors.Opaque(&wrapped{"mid",
-				&wrapped{"inner", nil}})}
+		opaque = &wrapped{
+			"outer",
+			errors.Opaque(&wrapped{
+				"mid",
+				&wrapped{"inner", nil},
+			}),
+		}
 	)
 	testCases := []struct {
 		err    error
@@ -89,7 +95,7 @@ func TestErrorFormatter(t *testing.T) {
 		fmt: "%+v",
 		want: "something:" +
 			"\n    github.com/go-faster/errors_test.TestErrorFormatter" +
-			"\n        .+/format_test.go:30" +
+			"\n        .+/format_test.go:32" +
 			"\n    something more",
 		regexp: true,
 	}, {

join_go120.go

@@ -5,4 +5,16 @@ package errors
 
 import "errors"
 
-var Join = errors.Join
+// Join returns an error that wraps the given errors.
+// Any nil error values are discarded.
+// Join returns nil if every value in errs is nil.
+// The error formats as the concatenation of the strings obtained
+// by calling the Error method of each element of errs, with a newline
+// between each string.
+//
+// A non-nil error returned by Join implements the Unwrap() []error method.
+//
+// Only available on go 1.20.x or superior.
+func Join(errs ...error) error {
+	return errors.Join(errs...)
+}

join_test.go → join_go120_test.go

@@ -1,3 +1,6 @@
+//go:build go1.20
+// +build go1.20
+
 package errors_test
 
 import (