Golang autocompletion

[Vadim Dmitriev]

Hello. I`m using golang to built ANTLRv4 autocompletion.

Here is golang runtime package for ANTLR: https://godoc.org/github.com/antlr/antlr4/runtime/Go/antlr

I created simple grammar:

grammar Simple;

start  : START (MIDDLE | END) ;

START  : 'start' ;
MIDDLE : 'middle' ;
END    : 'end' ;
WS     : [ \t] -> skip ;

And here my Go code:

listener := new(simple.BaseSimpleListener)

lexer := simple.NewSimpleLexer(input)
stream := antlr.NewCommonTokenStream(lexer, antlr.TokenDefaultChannel)
parser := simple.NewSimpleParser(stream)
parser.BuildParseTrees = true

tree := parser.Start()
antlr.ParseTreeWalkerDefault.Walk(listener, tree)

// Print expected tokens
fmt.Println(parser.GetExpectedTokens())

And when i run my code like this

go build && echo 'start' | ./autocompletion

I have panic:

line 1:5 missing {'middle', 'end'} at '<EOF>'
panic: Invalid state number.

But the most important thing is ErrorListener massage:

line 1:5 missing {'middle', 'end'} at '<EOF>

It means that ErrorListener works right. He can predict missing tokens.
How can I get this {'middle', 'end'} tokens without panic?

Thanks!