http_request.go

import (
	"net/http"
	"time"
	"log"
	"encoding/json"
	
	uuid "github.com/satori/go.uuid"
)

var (
 ConnectionFailed = "ConnectionFailed"
 UnexpectedResponse = "UnexpectedResponse"
 OK = "OK"
)

type SyntheticPayload struct {
	ID          string  `json:"id"`
	Type        string  `json:"type"`
	Timestamp   string  `json:"timestamp"`
}

func syntheticHttpRequest(url string, apiToken string) (string) {
	payload := SyntheticPayload {
		ID:         uuid.NewV4().String(),
		Type:       "BEACON",
		Timestamp:  time.Now().UTC().Format(time.RFC3339),
	}
	
	byt, err := json.Marshal(payload)
	if err != nil {
		log.Fatal("Could not parse the payload you specified. Please correct it!")
	}
	reader := bytes.NewReader(byt)
	
	req, err := http.NewRequest("POST", url, reader)
	if err != nil {
		log.Fatal(`[ERROR] Could not create a POST request. 
		This should not occur and there is something wrong with the code. Exiting.`)
	}
	req.Header.Add("Content-Type", "application/json")
	req.Header.Add("Authorization", "ApiToken "+apiToken)
	
	client := http.Client{}
	resp, err := client.Do(req)
	if err != nil {
		log.Println(`[ERROR] An request error occured. Is the service running 
			or have you specified the wrong url?`) 
		return ConnectionFailed
	} else if resp.StatusCode != 202 {
	  	return UnexpectedResponse
	}
	return OK
}

To avoid compare with strings and a more idiomatic way on Golang for errors should be:
Substitute this line:

var (
 ConnectionFailed = "ConnectionFailed"
 UnexpectedResponse = "UnexpectedResponse"
 OK = "OK"
)

for this:

// import "errors"
var (
    ConnectionFailed = errors.New("ConnectionFailed")
    UnexpectedResponse = errors.New("UnexpectedResponse")
)

and just change the method signature for this:

func syntheticHttpRequest(url string, apiToken string) error

and at the end of the function just return nil