docs: clarify description of go-bin-path output and its fallback behavior

action.yml

@@ -31,7 +31,7 @@ outputs:
   GOBIN:
     description: 'The value of `go env GOBIN`.'
   go-bin-path:
-    description: 'The base Go binary directory: `GOBIN`, otherwise `bin` under the first `GOPATH` entry.'
+    description: 'The base Go binary directory: the `GOBIN` value, otherwise `bin` under the first `GOPATH` entry when `GOBIN` is empty.'
   GOROOT:
     description: 'The value of `go env GOROOT`.'
   GOCACHE:
@@ -48,4 +48,4 @@ runs:
   using: 'node24'
   main: 'dist/setup/index.js'
   post: 'dist/cache-save/index.js'
-  post-if: success()
+  post-if: success()

docs/advanced-usage.md

@@ -431,7 +431,7 @@ Once Go is on the `PATH`, the action exposes the most commonly needed `go env` v
 | --- | --- |
 | `GOPATH` | Go workspace root; `bin` and `pkg/mod` live under it |
 | `GOBIN` | Go 1.27+ reports an implicit `$GOPATH/bin` default; earlier releases are empty unless `GOBIN` is set |
-| `go-bin-path` | The base Go binary directory (`GOBIN` or `$GOPATH/bin`), using the first `GOPATH` entry. Cross-compiled binaries go one level deeper, in `$GOPATH/bin/$GOOS_$GOARCH` |
+| `go-bin-path` | Uses `GOBIN`, or falls back to `bin` under the first `GOPATH` entry when `GOBIN` is empty. It normally matches `GOBIN` on Go 1.27+; the fallback is a convenience for earlier releases. When `GOBIN` is not explicitly set (in the environment or via `go env -w`), cross-compiled binaries go one level deeper, in `$GOPATH/bin/${GOOS}_${GOARCH}` |
 | `GOROOT` | Installation directory of the Go toolchain in use |
 | `GOCACHE` | Build cache directory |
 | `GOMODCACHE` | Module cache directory |