Make it into a real go module and fix CI

Author: evanphx

.github/workflows/go.yml

@@ -21,8 +21,5 @@ jobs:
     - name: Setup
       run: go get
 
-    - name: Build
-      run: go build -v ./...
-
     - name: Test
       run: go test -v ./...

go.mod

@@ -0,0 +1,8 @@
+module github.com/evanphx/json-patch
+
+go 1.14
+
+require (
+	github.com/jessevdk/go-flags v1.4.0
+	github.com/pkg/errors v0.9.1
+)

go.sum

@@ -0,0 +1,4 @@
+github.com/jessevdk/go-flags v1.4.0 h1:4IU2WS7AumrZ/40jfhf4QVDMsQwqA7VEHozFRrGARJA=
+github.com/jessevdk/go-flags v1.4.0/go.mod h1:4FA24M0QyGHXBuZZK/XkWh8h0e1EYbRYJSGM75WSRxI=
+github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
+github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=