Added Makefile to build releases

Author: jamietsao

.gitignore

@@ -1 +1,2 @@
+/bin
 main

Makefile

@@ -0,0 +1,21 @@
+# credit: https://vic.demuzere.be/articles/golang-makefile-crosscompile/
+PLATFORMS := darwin/386 darwin/amd64 linux/386 linux/amd64 windows/386 windows/amd64
+
+checkenv:
+ifndef TAG
+	$(error release TAG is required - e.g v0.1.0)
+endif
+
+temp = $(subst /, ,$@)
+os = $(word 1, $(temp))
+arch = $(word 2, $(temp))
+name = slack-multi-channel-invite
+longname = $(name)-$(TAG)-$(os)-$(arch)
+
+release: $(PLATFORMS)
+
+$(PLATFORMS): checkenv
+	GOOS=$(os) GOARCH=$(arch) go build -o 'bin/$(longname)/$(name)' main.go
+	cd bin/$(longname) && zip $(longname).zip $(name)
+
+.PHONY: checkenv release $(PLATFORMS) zip

README.md

@@ -13,7 +13,9 @@ Enjoy!
     - `channels.read`
     - `channels.write`
 3. Install app to your workspace which will generate a new OAuth Access Token
-4. Install this script via `go get github.com/jamietsao/slack-multi-channel-invite`
+4. Download script:
+    - If you have Go installed: `go get github.com/jamietsao/slack-multi-channel-invite`
+    - Else download the binary directly: https://github.com/jamietsao/slack-multi-channel-invite/releases
 5. Run script:
 
 `slack-multi-channel-invite -api_token=<oauth-access-token> -channels=foo,bar,baz -user_email=steph@curry.com`