cmd/go/internal/get: improve -insecure deprecation docs

Updates #37519

Author: witchard

src/cmd/go/alldocs.go

@@ -46,8 +46,8 @@ before resolving dependencies or building the code.
 The -insecure flag permits fetching from repositories and resolving
 custom domains using insecure schemes such as HTTP. Use with caution.
 This flag is deprecated and will be removed in a future version of go.
-The GOINSECURE environment variable is usually a better alternative, since
-it provides control over which modules may be retrieved using an insecure
+The GOINSECURE environment variable should be used instead, since it
+provides control over which modules may be retrieved using an insecure
 scheme. See 'go help environment' for details.
 
 The -t flag instructs get to also download the packages required to build

src/cmd/go/internal/get/get.go

@@ -117,11 +117,12 @@ this automatically as well.
 The -insecure flag permits fetching from repositories and resolving
 custom domains using insecure schemes such as HTTP. Use with caution.
 This flag is deprecated and will be removed in a future version of go.
-The GOINSECURE environment variable is usually a better alternative, since
-it provides control over which modules may be retrieved using an insecure
-scheme. It should be noted that the -insecure flag also turns the module
-checksum validation off. GOINSECURE does not do that, use GONOSUMDB.
-See 'go help environment' for details.
+The GOINSECURE environment variable should be used instead, since it
+provides control over which modules may be retrieved using an insecure
+scheme. Unlike the -insecure flag, GOINSECURE does not disable module
+sum validation using the checksum database. The GOPRIVATE or GONOSUMDB
+environment variable may be used instead. See 'go help environment'
+for details.
 
 The second step is to download (if needed), build, and install
 the named packages.