Make error reporting verbose

Without proper error reporting we can't tell why something failed.
This commit adds wrapping of Redis errors with our error messages.

go.mod

@@ -6,5 +6,6 @@ require (
 	github.com/go-redis/redis v6.15.2+incompatible
 	github.com/onsi/ginkgo v1.8.0 // indirect
 	github.com/onsi/gomega v1.5.0 // indirect
+	github.com/pkg/errors v0.8.1
 	github.com/spf13/pflag v1.0.3
 )

go.sum

@@ -11,6 +11,8 @@ github.com/onsi/ginkgo v1.8.0 h1:VkHVNpR4iVnU8XQR6DBm8BqYjN7CRzw+xKUbVVbbW9w=
 github.com/onsi/ginkgo v1.8.0/go.mod h1:lLunBs/Ym6LB5Z9jYTR76FiuTmxDTDusOGeTQH+WWjE=
 github.com/onsi/gomega v1.5.0 h1:izbySO9zDPmjJ8rDjLvkA2zJHIo+HkYXHnf7eN7SSyo=
 github.com/onsi/gomega v1.5.0/go.mod h1:ex+gbHU/CVuBBDIJjb2X0qEXbFg53c61hWP/1CpauHY=
+github.com/pkg/errors v0.8.1 h1:iURUrRGxPUNPdy5/HRSm+Yj6okJ6UtLINN0Q9M4+h3I=
+github.com/pkg/errors v0.8.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
 github.com/spf13/pflag v1.0.3 h1:zPAT6CGy6wXeQ7NtTnaTerfKOsV6V6F8agHXFiazDkg=
 github.com/spf13/pflag v1.0.3/go.mod h1:DYY7MBk1bdzusC3SYhjObp+wFpr4gzcvqqNjLnInEg4=
 golang.org/x/net v0.0.0-20180906233101-161cd47e91fd h1:nTDtHvHSdCn1m6ITfMRqtOd/9+7a3s8RBNOZ3eYZzJA=

main.go

@@ -2,18 +2,18 @@ package main
 
 import (
 	"fmt"
-	"log"
 	"os"
 
 	"github.com/go-redis/redis"
+	"github.com/pkg/errors"
 	"github.com/spf13/pflag"
 )
 
 // exec executes pipeline and ignore error by merely printing it
 func exec(pipe redis.Pipeliner) {
 	_, err := pipe.Exec()
 	if err != nil {
-		log.Println(err)
+		errors.Wrap(err, "pipeline exec failed")
 	}
 }
 
@@ -64,7 +64,7 @@ func main() {
 		// Grab the next portion of keys
 		keys, cursor, err = redisdb.Scan(cursor, pattern, count).Result()
 		if err != nil {
-			log.Println(err)
+			errors.Wrap(err, "scan failed")
 			break
 		}