docs: fix variable assignment mistake on example code

examples/Cassandra.md

@@ -2,7 +2,7 @@
 var db *mgo.Session
 var err error
 
-pool, err = dockertest.NewPool("")
+pool, err := dockertest.NewPool("")
 if err != nil {
     log.Fatalf("Could not connect to docker: %s", err)
 }

examples/Minio.md

@@ -2,7 +2,7 @@
 var minioClient *minio.Client
 var err error
 
-pool, err = dockertest.NewPool("")
+pool, err := dockertest.NewPool("")
 if err != nil {
     log.Fatalf("Could not connect to docker: %s", err)
 }

examples/MongoDB.md

@@ -2,7 +2,7 @@
 var db *mgo.Session
 var err error
 
-pool, err = dockertest.NewPool("")
+pool, err := dockertest.NewPool("")
 if err != nil {
     log.Fatalf("Could not connect to docker: %s", err)
 }

examples/MySQL.md

@@ -1,7 +1,7 @@
 ```go
 var db *sql.DB
 var err error
-pool, err = dockertest.NewPool("")
+pool, err := dockertest.NewPool("")
 pool.MaxWait = time.Minute * 2
 if err != nil {
     log.Fatalf("Could not connect to docker: %s", err)

examples/Redis.md

@@ -1,7 +1,7 @@
 ```go
 var db *redis.Client
 var err error
-pool, err = dockertest.NewPool("")
+pool, err := dockertest.NewPool("")
 if err != nil {
     log.Fatalf("Could not connect to docker: %s", err)
 }

examples/RethinkDB.md

@@ -1,7 +1,7 @@
 ```go
 var session *r.Session
 var err error
-pool, err = dockertest.NewPool("")
+pool, err := dockertest.NewPool("")
 if err != nil {
     log.Fatalf("Could not connect to docker: %s", err)
 }