Adds support for build on GOOS=js (#1614)

Signed-off-by: Takeshi Yoneda <t.y.mathetake@gmail.com>

Makefile

@@ -214,6 +214,8 @@ check:
 #
 # Ensure we build on plan9. See #1578
 	@GOARCH=amd64 GOOS=plan9 go build ./...
+# Ensure we build on gojs. See #1526. TODO: add GOOS=wasi as well.
+	@GOARCH=wasm GOOS=js go build ./...
 # Ensure we build on windows:
 	@GOARCH=amd64 GOOS=windows go build ./...
 # Ensure we build on an arbitrary operating system:

internal/sock/sock_plan9.go

@@ -1,8 +0,0 @@
-package sock
-
-// plan9 doesn't declare these constants
-const (
-	SHUT_RD = iota
-	SHUT_RDWR
-	SHUT_WR
-)

internal/sock/sock_supported.go

@@ -1,4 +1,4 @@
-//go:build !plan9
+//go:build !plan9 && !js
 
 package sock
 

internal/sock/sock_unsupported.go

@@ -0,0 +1,10 @@
+//go:build plan9 || js
+
+package sock
+
+// plan9/js doesn't declare these constants
+const (
+	SHUT_RD = 1 << iota
+	SHUT_WR
+	SHUT_RDWR = SHUT_RD | SHUT_WR
+)