sdk.bzl: include go.env since 1.21.0

Include go.env file in the root of the sdk repo starting from Go 1.21.0.

WORKSPACE

@@ -5,7 +5,7 @@ load("@io_bazel_rules_go//go:deps.bzl", "go_register_toolchains", "go_rules_depe
 
 go_rules_dependencies()
 
-go_register_toolchains(version = "1.20.7")
+go_register_toolchains(version = "1.21.0")
 
 http_archive(
     name = "com_google_protobuf",

go/private/BUILD.sdk.bazel

@@ -80,6 +80,7 @@ filegroup(
         "bin/go*",
         "src/**",
         "pkg/**",
+        {goenv}
     ]),
 )
 

go/private/sdk.bzl

@@ -478,6 +478,9 @@ def _sdk_build_file(ctx, platform, version, experiments):
         if not "nocoverageredesign" in experiments and not "coverageredesign" in experiments:
             experiments = experiments + ["nocoverageredesign"]
 
+    # TODO(sluongng): Remove this once we drop support for Go 1.20
+    include_go_env = pv[1] >= 21
+
     ctx.template(
         "BUILD.bazel",
         ctx.path(ctx.attr._sdk_build_file),
@@ -488,6 +491,7 @@ def _sdk_build_file(ctx, platform, version, experiments):
             "{exe}": ".exe" if goos == "windows" else "",
             "{version}": version,
             "{experiments}": repr(experiments),
+            "{goenv}": "\"go.env\"," if include_go_env else "",
         },
     )