In a Golang framework shared between several goroutines, are non-members in need of mutex protection?

Question

I have one Golang structure shared between several goroutines. For concurrent access to structure members, there is mutex sync.RWMutex. Does a single goroutin call for a structural element, do I need protection from the mutex?

For example, in the code below, a single goroutine author accesses the shared.exclusiveCounter member without blocking protection. Is this correct / safe? Or is there a need for a mutec because the entire structure is drawn by several larynxes through a common index?

package main

import (
    "fmt"
    "sync"
    "time"
)

func main() {
    s := &shared{mutex: &sync.RWMutex{}}

    readerDone := make(chan int)
    writerDone := make(chan int)

    go reader(s, readerDone)
    go writer(s, writerDone)

    <-readerDone
    <-writerDone
}

type shared struct {
    mutex            *sync.RWMutex
    sharedCounter    int // member shared between multiple goroutines, protected by mutex
    exclusiveCounter int // member exclusive of one goroutine -- is mutex needed?
}

func (s *shared) readCounter() int {
    defer s.mutex.RUnlock()
    s.mutex.RLock()
    return s.sharedCounter
}

func (s *shared) setCounter(i int) {
    defer s.mutex.Unlock()
    s.mutex.Lock()
    s.sharedCounter = i
}

func reader(s *shared, done chan<- int) {
    for {
        time.Sleep(2 * time.Second)
        counter := s.readCounter()
        fmt.Printf("reader: read counter=%d\n", counter)
        if counter > 5 {
            break
        }
    }
    fmt.Printf("reader: exiting\n")
    done <- 1
}

func writer(s *shared, done chan<- int) {
    s.exclusiveCounter = 0
    for {
        time.Sleep(1 * time.Second)
        s.exclusiveCounter++
        fmt.Printf("writer: writing counter=%d\n", s.exclusiveCounter)
        s.setCounter(s.exclusiveCounter)
        if s.exclusiveCounter > 5 {
            break
        }
    }
    fmt.Printf("writer: exiting\n")
    done <- 1
}

Run it on the playground

Answer 1

goroutine struct, . , , ( , ), , , , , .

Answer 2

, , int *, atomic.*

type shared struct {
    sharedCounter    int64 // member shared between multiple goroutines, protected by mutex
    exclusiveCounter int64 // member exclusive of one goroutine -- is mutex needed?
}

func (s *shared) readCounter() int64 {
    return atomic.LoadInt64(&s.sharedCounter)
}

func (s *shared) setCounter(i int64) {
    atomic.StoreInt64(&s.sharedCounter, i)
}

playground