如何减少go嵌套函数调用中的参数数量

Question

I have a go Calltree which is structured as follows:

// state is a common struct shared among all "instances" of MyType - simulating member variables for an Interface
(s MyType) Run(state *State){ // called from outside
  // define goroutines that fetch something via http
  HTTPCallback(){ // runs on every http response
    parseData(record, outputChan)
  }
}
(s MyType) parseData(rec []string, outputChan chan(interface{})){
  // doesn't need anything from "state" so far
  doIdMapping(string) 
}


doIdMapping(key) { 
   return state.Map[key] 
}

Is there a way of getting access to the Map (which is completely constant) without being forced to pass the "state" through HTTPCallback and all the goroutines above which end up in calling HTTPCallback?

This is not only bad for a clear code but also is bad when it comes to testing. All the intermediate functions carry around that struct pointer which they don't even need to depend on. Did I miss something about the language design of go? :/

Answer 1

If all of this is within a single package you can simply declare State at the package level and use it everywhere. For example;

package myHttpClient

import (
    "allthatstuff"
)

state State // not exported but available everywhere in 'myHttpClient'
ExternState State // exported so anyone importing myHttpClient can do myHttpClient.ExternState