go/build: document when Context.BuildTags is used.
Context.BuildTags is not set when you read go/build.Default.BuildTags.
It's only used by (*BuildTags).Import, etc.
Fixes: #27320
Change-Id: I97e5f1923c410b48f70be8c15938a7e04a178e3f
Reviewed-on: https://go-review.googlesource.com/c/131975
Reviewed-by: Ian Lance Taylor <iant@golang.org>
diff --git a/src/go/build/build.go b/src/go/build/build.go
index 5e683ae..0fa6720 100644
--- a/src/go/build/build.go
+++ b/src/go/build/build.go
@@ -43,6 +43,7 @@
// Clients creating a new context may customize BuildTags, which
// defaults to empty, but it is usually an error to customize ReleaseTags,
// which defaults to the list of Go releases the current release is compatible with.
+ // BuildTags is not set for the Default build Context.
// In addition to the BuildTags and ReleaseTags, build constraints
// consider the values of GOARCH and GOOS as satisfied tags.
// The last element in ReleaseTags is assumed to be the current release.
