func forwardRequest()

in main.go [88:166]
54 lines of code
13 McCabe index (conditional complexity)

func forwardRequest(req *http.Request, reqSourceIP string, reqDestionationPort string, body []byte) {

	// if percentage flag is not 100, then a percentage of requests is skipped
	if *fwdPerc != 100 {
		var uintForSeed uint64

		if *fwdBy == "" {
			// if percentage-by is empty, then forward only a certain percentage of requests
			var b [8]byte
			_, err := crypto_rand.Read(b[:])
			if err != nil {
				log.Println("Error generating crypto random unit for seed", ":", err)
				return
			}
			// uintForSeed is random
			uintForSeed = binary.LittleEndian.Uint64(b[:])
		} else {
			// if percentage-by is not empty, then forward only requests from a certain percentage of headers/remoteaddresses
			strForSeed := ""
			if *fwdBy == "header" {
				strForSeed = req.Header.Get(*fwdHeader)
			} else {
				strForSeed = reqSourceIP
			}
			crc64Table := crc64.MakeTable(0xC96C5795D7870F42)
			// uintForSeed is derived from strForSeed
			uintForSeed = crc64.Checksum([]byte(strForSeed), crc64Table)
		}

		// generate a consistent random number from the variable uintForSeed
		math_rand.Seed(int64(uintForSeed))
		randomPercent := math_rand.Float64() * 100
		// skip a percentage of requests
		if randomPercent > *fwdPerc {
			return
		}
	}

	// create a new url from the raw RequestURI sent by the client
	url := fmt.Sprintf("%s%s", string(*fwdDestination), req.RequestURI)

	// create a new HTTP request
	forwardReq, err := http.NewRequest(req.Method, url, bytes.NewReader(body))
	if err != nil {
		return
	}

	// add headers to the new HTTP request
	for header, values := range req.Header {
		for _, value := range values {
			forwardReq.Header.Add(header, value)
		}
	}

	// Append to X-Forwarded-For the IP of the client or the IP of the latest proxy (if any proxies are in between)
	// https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-Forwarded-For
	forwardReq.Header.Add("X-Forwarded-For", reqSourceIP)
	// The three following headers should contain 1 value only, i.e. the outermost port, protocol, and host
	// https://tools.ietf.org/html/rfc7239#section-5.4
	if forwardReq.Header.Get("X-Forwarded-Port") == "" {
		forwardReq.Header.Set("X-Forwarded-Port", reqDestionationPort)
	}
	if forwardReq.Header.Get("X-Forwarded-Proto") == "" {
		forwardReq.Header.Set("X-Forwarded-Proto", "http")
	}
	if forwardReq.Header.Get("X-Forwarded-Host") == "" {
		forwardReq.Header.Set("X-Forwarded-Host", req.Host)
	}

	// Execute the new HTTP request
	httpClient := &http.Client{}
	resp, rErr := httpClient.Do(forwardReq)
	if rErr != nil {
		// log.Println("Forward request error", ":", err)
		return
	}

	defer resp.Body.Close()
}