Have anyone got the plan for uploading file?

i can't find the method to upload file, i have saw the apollo upload examples, and i found the graphql-js is so different from graphql-go.

```go
var Upload = graphql.NewScalar(graphql.ScalarConfig{
Name: "Upload",
Description: "The `Upload` scalar type represents a file upload promise that resolves " +
"an object containing `stream`, `filename`, `mimetype` and `encoding`.",
Serialize: coerceFile,
ParseValue: coerceFile,
ParseLiteral: func(valueAST ast.Value) interface{} {
fmt.Println("wrong func")
return nil
},
})

func coerceFile(value interface{}) interface{} {
return value
}
```

i write the scalar for uploading, but i found it doesn't work well