From d3008588c66317795bedc0d27abc29d85976cfaa Mon Sep 17 00:00:00 2001
From: Manlio Perillo <manlio.perillo@gmail.com>
Date: Mon, 11 Mar 2019 17:33:41 +0100
Subject: [PATCH] cmd/go: add trust module build mode

Add the trust module build mode for interoperability with operating
systems package managers.
---
 src/cmd/go/internal/modfetch/fetch.go | 4 ++++
 src/cmd/go/internal/work/build.go     | 2 +-
 src/cmd/go/internal/work/init.go      | 2 +-
 3 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/cmd/go/internal/modfetch/fetch.go b/src/cmd/go/internal/modfetch/fetch.go
index 1d6969ea3e..5b04f40e43 100644
--- a/src/cmd/go/internal/modfetch/fetch.go
+++ b/src/cmd/go/internal/modfetch/fetch.go
@@ -281,6 +281,10 @@ var goSum struct {
 // It reports whether use of go.sum is now enabled.
 // The goSum lock must be held.
 func initGoSum() bool {
+	if cfg.BuildMod == "trust" {
+		// Trust me!
+		return false
+	}
 	if GoSumFile == "" {
 		return false
 	}
diff --git a/src/cmd/go/internal/work/build.go b/src/cmd/go/internal/work/build.go
index 145b87513a..ab8d31832c 100644
--- a/src/cmd/go/internal/work/build.go
+++ b/src/cmd/go/internal/work/build.go
@@ -99,7 +99,7 @@ and test commands:
 		link against shared libraries previously created with
 		-buildmode=shared.
 	-mod mode
-		module download mode to use: readonly or vendor.
+		module download mode to use: readonly, trust or vendor.
 		See 'go help modules' for more.
 	-pkgdir dir
 		install and load all packages from dir instead of the usual locations.
diff --git a/src/cmd/go/internal/work/init.go b/src/cmd/go/internal/work/init.go
index 3381ab544c..ef7c15a9c2 100644
--- a/src/cmd/go/internal/work/init.go
+++ b/src/cmd/go/internal/work/init.go
@@ -240,7 +240,7 @@ func buildModeInit() {
 	switch cfg.BuildMod {
 	case "":
 		// ok
-	case "readonly", "vendor":
+	case "readonly", "trust", "vendor":
 		if load.ModLookup == nil && !inGOFLAGS("-mod") {
 			base.Fatalf("build flag -mod=%s only valid when using modules", cfg.BuildMod)
 		}
--
2.21.0