graphite: refactor error handling

[ifireice]

Removed Logger interface and make error handling more flexible.

For example, we could use our own logger implementation and have more control over the execution flow

package main

import (
	"context"
	"time"

	"github.com/prometheus/client_golang/prometheus"
	"github.com/prometheus/client_golang/prometheus/graphite"
	"go.uber.org/zap"
)

func main() {
	logger, _ := zap.NewProduction()
	defer logger.Sync()

	ctx := context.Background()
	ctx, cancel := context.WithCancel(ctx)
	defer cancel()

	c := &Config{
			URL:              "graphite.example.org:3099",
			Gatherer:         prometheus.DefaultGatherer,
			Prefix:           "prefix",
			Interval:          5 * time.Second,
			Timeout:           2 * time.Second,
			ErrorHandling:     testCase.errorHandling,
			ErrorCallbackFunc: func(err error) {  if err != nil { logger.Error("run", zap.Error(err)); cancel() } },
		}


	b, err := graphite.NewBridge(c)
	if err != nil {
			t.Fatal(err)
		}

	b.Run(ctx)
}