Go Target:how Exit when Error occurred

I have search [antlr4-discussion google group](https://groups.google.com/forum/#!forum/antlr-discussion) and stackoverflow ,this is no way to solve this.

1. I use the example [JSON.g4](https://github.com/antlr/grammars-v4/tree/master/json).
2. execute antlr4
antlr4 -Dlanguage=Go -o parser JSON.g4
3. the main.go
```
package main

import (
"github.com/antlr/antlr4/runtime/Go/antlr"
"./parser"
"fmt"
)

type TreeShapeListener struct {
*parser.BaseJSONListener
}

func NewTreeShapeListener() *TreeShapeListener {
return new(TreeShapeListener)
}

func (this *TreeShapeListener) EnterEveryRule(ctx antlr.ParserRuleContext) {
fmt.Println(ctx.GetText())
}

func main() {
str:=`{"a":1}!`
input := new(antlr.FileStream)
input.InputStream = antlr.NewInputStream(str)
lexer := parser.NewJSONLexer(input)
stream := antlr.NewCommonTokenStream(lexer,0)
p := parser.NewJSONParser(stream)
p.AddErrorListener(antlr.NewDiagnosticErrorListener(true))
p.BuildParseTrees = true
tree := p.Json()
antlr.ParseTreeWalkerDefault.Walk(NewTreeShapeListener(), tree)
}
```
4.
`go run main.go`
I want the the error message and hope exit when error occurred this is the output:
```
root@iZj6ca7mzaes6eiy2p6fnsZ:~/grammars-v4/json# go run main.go
line 1:7 token recognition error at: '!'
{"a":1}
{"a":1}
{"a":1}
"a":1
1
```

Start with main.go and the JSON.g4 example, then inspect how the generated Go parser and Go runtime report the trailing '!'. Run `go run main.go` to reproduce the diagnostic and tree-walking output. Done means the error is exposed to the caller and the requested behavior of stopping after an error is defined and demonstrated.

Written by the indexing model from the issue text.