parseRequestHeader fatal: concurrent map iteration and map write

[shoteen-lee]

`

    method = strings.ToUpper(method)
client, uri := getClient(c, uri, withLog, method)

for _, f := range options {
	f(client)
}

r := client.R().SetContext(c)

//default header
if method == resty.MethodPost || method == resty.MethodPut {
	r.SetHeader("content-type", "application/json")
}
for h, v := range headers {
	r.SetHeader(h, v)
}

// request id
if !strings.Contains(uri, common.RequestId) {
	tmpReqId := common.GetRequestId(c)
	if tmpReqId == "" {
		tmpReqId = uuid.NewString()
		c = context.WithValue(c, common.RequestId, tmpReqId)
	}
	r.SetQueryParam(common.RequestId, tmpReqId)
}`

When the project starts, a resty client is initialized. This client is reused for requests, and headers are set on the client using client.R() when initializing a request. However, there are occasional occurrences of concurrent map iteration and map write. Why does this happen?