update minimum supported version of Go to 1.12

Go 1.11 is not supported upstream and it also breaks our precious VM for some
reason, so use better versions of Go. Fixes #384.

.circleci/config.yml

@@ -3,11 +3,6 @@ orbs:
   codecov: codecov/codecov@1.0.5
 
 executors:
-  go1_11:
-    docker:
-      - image: circleci/golang:1.11
-        environment:
-          GO111MODULE: "on"
   go1_12:
     docker:
       - image: circleci/golang:1.12
@@ -54,14 +49,6 @@ jobs:
           name: go-vet
           command: go vet ./...
 
-  test_1_11:
-    working_directory: /go/src/github.com/CityOfZion/neo-go
-    executor: go1_11
-    steps:
-      - checkout
-      - gomod
-      - run: go test -v -race ./...
-
   test_1_12:
     working_directory: /go/src/github.com/CityOfZion/neo-go
     executor: go1_12
@@ -123,10 +110,6 @@ workflows:
           filters:
             tags:
               only: v/[0-9]+\.[0-9]+\.[0-9]+/
-      - test_1_11:
-          filters:
-            tags:
-              only: v/[0-9]+\.[0-9]+\.[0-9]+/
       - test_1_12:
           filters:
             tags:

.travis.yml

@@ -1,6 +1,5 @@
 language: go
 go:
-  - 1.11.x
   - 1.12.x
 env:
   - GO111MODULE=on

README.md

@@ -31,7 +31,7 @@ A complete toolkit for the NEO blockchain, including:
 
 ## Installation
 
-Go: 1.11+
+Go: 1.12+
 
 Install dependencies.