Building firectl requires at least Go 1.14

Signed-off-by: Volker Simonis <volker.simonis@gmail.com>

Author: simonis

Makefile

@@ -31,7 +31,7 @@ else
 endif
 
 build-in-docker:
-	docker run --rm -v $(CURDIR):/firectl --workdir /firectl golang:1.12 make
+	docker run --rm -v $(CURDIR):/firectl --workdir /firectl golang:1.14 make
 
 test:
 	go test -v ./...

README.md

@@ -13,8 +13,8 @@ Building
 
 The default Makefile rule executes `go build` and relies on the Go toolchain
 installed on your computer.
-_We use [go modules](https://github.com/golang/go/wiki/Modules), so you need to
-build with Go 1.11 or newer._
+_We use [go modules](https://github.com/golang/go/wiki/Modules), and building
+requires Go 1.14 or newer._
 
 If you do not have a new-enough Go toolchain installed, you can use `make
 build-in-docker`.  This rule creates a temporary Docker container which builds