cmd/cgo: close file

Change-Id: Ia70edc8ba22e31e498fe07946db41882804bd39f
GitHub-Last-Rev: 280232e879965b34fae3aa02e6215eff5bd7be46
GitHub-Pull-Request: golang/go#39120
Reviewed-on: https://go-review.googlesource.com/c/go/+/234317
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
diff --git a/src/cmd/cgo/out.go b/src/cmd/cgo/out.go
index 4064f0a..50d2811 100644
--- a/src/cmd/cgo/out.go
+++ b/src/cmd/cgo/out.go
@@ -243,6 +243,7 @@
 		if err != nil {
 			fatalf("%s", err)
 		}
+		defer fgcch.Close()
 		_, err = io.Copy(fexp, fgcch)
 		if err != nil {
 			fatalf("%s", err)