cmd/go: add GOPRIVATE environment variable

It is too confusing to have to set GONOSUMDB and GONOPROXY
in common use cases, but one cannot be guaranteed to be a
subset of the other.

This CL adds GOPRIVATE, which takes the same kind of pattern list
but is defined as "these patterns are private (non-public) modules".
Today the implication is that GOPRIVATE is the default setting for
GONOSUMDB and GONOPROXY. If there are other accommodations
to make for private packages in the future or in other tools,
having this clear statement of intent will let us do that.
(For example maybe an IDE integration would hyperlink an import
path to godoc.org; consulting GOPRIVATE would be a reasonable
way to decide not to do that for certain imports. In contrast,
consulting GONOPROXY or GONOSUMDB clearly would not.)

Fixes #32184.

Change-Id: If54c12d353c7a0a5c0e0273764140cce3c154a02
Reviewed-on: https://go-review.googlesource.com/c/go/+/181719
Run-TryBot: Russ Cox <[email protected]>
Reviewed-by: Bryan C. Mills <[email protected]>
Reviewed-by: Jay Conrod <[email protected]>
TryBot-Result: Gobot Gobot <[email protected]>

Author: rsc

src/cmd/go/alldocs.go

@@ -265,6 +265,7 @@ var knownEnv = `
 	GOOS
 	GOPATH
 	GOPPC64
+	GOPRIVATE
 	GOPROXY
 	GOROOT
 	GOSUMDB
@@ -291,30 +292,13 @@ var (
 	GOPPC64  = envOr("GOPPC64", fmt.Sprintf("%s%d", "power", objabi.GOPPC64))
 	GOWASM   = envOr("GOWASM", fmt.Sprint(objabi.GOWASM))
 
-	GOPROXY   = goproxy()
-	GOSUMDB   = gosumdb()
-	GONOPROXY = Getenv("GONOPROXY")
-	GONOSUMDB = Getenv("GONOSUMDB")
+	GOPROXY   = envOr("GOPROXY", "https://proxy.golang.org,direct")
+	GOSUMDB   = envOr("GOSUMDB", "sum.golang.org")
+	GOPRIVATE = Getenv("GOPRIVATE")
+	GONOPROXY = envOr("GONOPROXY", GOPRIVATE)
+	GONOSUMDB = envOr("GONOSUMDB", GOPRIVATE)
 )
 
-func goproxy() string {
-	v := Getenv("GOPROXY")
-	if v != "" {
-		return v
-	}
-
-	return "https://proxy.golang.org,direct"
-}
-
-func gosumdb() string {
-	v := Getenv("GOSUMDB")
-	if v != "" {
-		return v
-	}
-
-	return "sum.golang.org"
-}
-
 // GetArchEnv returns the name and setting of the
 // GOARCH-specific architecture environment variable.
 // If the current architecture has no GOARCH-specific variable,

src/cmd/go/internal/cfg/cfg.go

@@ -79,6 +79,7 @@ func MkEnv() []cfg.EnvVar {
 		{Name: "GONOSUMDB", Value: cfg.GONOSUMDB},
 		{Name: "GOOS", Value: cfg.Goos},
 		{Name: "GOPATH", Value: cfg.BuildContext.GOPATH},
+		{Name: "GOPRIVATE", Value: cfg.GOPRIVATE},
 		{Name: "GOPROXY", Value: cfg.GOPROXY},
 		{Name: "GOROOT", Value: cfg.GOROOT},
 		{Name: "GOSUMDB", Value: cfg.GOSUMDB},

src/cmd/go/internal/envcmd/env.go

@@ -510,19 +510,16 @@ General-purpose environment variables:
 		For more details see: 'go help gopath'.
 	GOPROXY
 		URL of Go module proxy. See 'go help modules'.
-	GONOPROXY
+	GOPRIVATE, GONOPROXY, GONOSUMDB
 		Comma-separated list of glob patterns (in the syntax of Go's path.Match)
-		of module path prefixes that should always be fetched directly, ignoring
-		the GOPROXY setting. See 'go help modules'.
+		of module path prefixes that should always be fetched directly
+		or that should not be compared against the checksum database.
+		See 'go help module-private'.
+	GOROOT
+		The root of the go tree.
 	GOSUMDB
 		The name of checksum database to use and optionally its public key and
 		URL. See 'go help module-auth'.
-	GONOSUMDB
-		Comma-separated list of glob patterns (in the syntax of Go's path.Match)
-		of module path prefixes that should not be compared against the checksum
-		database. See 'go help module-auth'.
-	GOROOT
-		The root of the go tree.
 	GOTMPDIR
 		The directory where the go command will write
 		temporary source files, packages, and binaries.