String interning in Golang

intern.go

package intern

import (
  "sync"
)

type Pool struct {
  sync.RWMutex
  lookup map[string]string
}

func New() *Pool {
  return &Pool{lookup: make(map[string]string)}
}

func (p *Pool) Intern(s string) string {
  p.RLock()
  ss, found := p.lookup[s]
  p.RUnlock()
  if found { 
    return ss 
  }
  
  /* 
  if we had p.RLockToLock() - i.e. something that either atomically upgrades the
  RLock to a Lock and returns true or does RUnlock+Lock and returns false - we
  could do this instead of the following:
  
  if !p.RLockToLock() {
    ss, found := p.lookup[s]
    if found {
      s = ss
      goto unlock_and_return
    }
  }
  p.Lookup[s] = s
  
unlock_and_return:
  p.Unlock()
  return s
  
  */
  
  p.Lock()
  ss, found := p.lookup[s]
  if !found {
    p.lookup[s] = s
    ss = s
  }
  p.Unlock()
  return ss
}