{"id":1090,"date":"2026-08-17T00:43:03","date_gmt":"2026-08-17T00:43:03","guid":{"rendered":"https:\/\/www.devopsschool.com\/tutorials\/?p=1090"},"modified":"2026-08-17T08:31:27","modified_gmt":"2026-08-17T08:31:27","slug":"go-concurrency-management-made-simple","status":"publish","type":"post","link":"https:\/\/www.devopsschool.com\/tutorials\/go-concurrency-management-made-simple\/","title":{"rendered":"Go Concurrency Management Made Simple"},"content":{"rendered":"\n
This tutorial covers:<\/p>\n\n\n\n
\n
sync.WaitGroup<\/code><\/li>\n\n\n\n
sync.Mutex<\/code><\/li>\n\n\n\n
Goroutine leaks<\/li>\n\n\n\n
context.Context<\/code><\/li>\n\n\n\n
Cancellation<\/li>\n\n\n\n
Timeouts<\/li>\n\n\n\n
Graceful shutdown<\/li>\n<\/ol>\n\n\n\n
The goal is:<\/p>\n\n\n\n
\n
One concept \u2192 one purpose \u2192 one complete runnable example.<\/strong><\/p>\n<\/blockquote>\n\n\n\n
Every example is independent.<\/p>\n\n\n\n
Save any example as:<\/p>\n\n\n\n
main.go<\/code><\/pre>\n\n\n\n
and run:<\/p>\n\n\n\n
go run main.go<\/code><\/pre>\n\n\n\n\n\n\n\n
0. First Understand the Big Picture<\/h1>\n\n\n\n
These concepts solve different concurrency problems<\/strong>.<\/p>\n\n\n\n
flowchart TD\n A[Concurrent Application]\n\n A --> B[WaitGroup]\n A --> C[Mutex]\n A --> D[Context]\n\n B --> B1[Wait for goroutines]\n\n C --> C1[Protect shared data]\n\n D --> D1[Cancellation]\n D --> D2[Timeout]\n\n D1 --> E[Stop goroutines safely]\n D2 --> E\n\n E --> F[Graceful Shutdown]\n\n A --> G[Prevent Goroutine Leaks]<\/code><\/pre>\n\n\n\n
The most important thing to remember:<\/p>\n\n\n\n
\n
WaitGroup waits. Mutex protects. Context communicates when work should stop.<\/strong><\/p>\n<\/blockquote>\n\n\n\n\n\n\n\n
1. sync.WaitGroup<\/code><\/h1>\n\n\n\n
What?<\/h2>\n\n\n\n
A WaitGroup<\/code> lets one goroutine wait until other goroutines have finished.<\/p>\n\n\n\n
package main\n\nimport (\n\t\"fmt\"\n\t\"sync\"\n\t\"time\"\n)\n\nfunc worker(id int, wg *sync.WaitGroup) {\n\n\t\/\/ Done() decreases the WaitGroup counter by 1.\n\t\/\/ defer makes sure it runs when worker finishes.\n\tdefer wg.Done()\n\n\tfmt.Println(\"Worker\", id, \"started\")\n\n\t\/\/ Simulate some work.\n\ttime.Sleep(500 * time.Millisecond)\n\n\tfmt.Println(\"Worker\", id, \"finished\")\n}\n\nfunc main() {\n\n\tvar wg sync.WaitGroup\n\n\t\/\/ Start 3 workers.\n\tfor i := 1; i <= 3; i++ {\n\n\t\t\/\/ Tell WaitGroup:\n\t\t\/\/ one more goroutine is starting.\n\t\twg.Add(1)\n\n\t\tgo worker(i, &wg)\n\t}\n\n\tfmt.Println(\"Main is waiting...\")\n\n\t\/\/ Wait until all workers call Done().\n\twg.Wait()\n\n\tfmt.Println(\"All workers finished\")\n}<\/code><\/pre>\n\n\n\n
Possible output:<\/p>\n\n\n\n
Main is waiting...\nWorker 1 started\nWorker 3 started\nWorker 2 started\nWorker 1 finished\nWorker 2 finished\nWorker 3 finished\nAll workers finished<\/code><\/pre>\n\n\n\n
The worker order may change.<\/p>\n\n\n\n
That is normal.<\/p>\n\n\n\n
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Mental Model<\/h2>\n\n\n\n
flowchart LR\n M[main] --> W1[Worker 1]\n M --> W2[Worker 2]\n M --> W3[Worker 3]\n\n W1 --> WG[WaitGroup]\n W2 --> WG\n W3 --> WG\n\n WG --> C[main continues]<\/code><\/pre>\n\n\n\n\n\n\n\n
Remember<\/h2>\n\n\n\n
WaitGroup<\/code>:<\/p>\n\n\n\n
\n
Waits for goroutines.<\/strong><\/p>\n<\/blockquote>\n\n\n\n
It does not<\/strong> protect shared data.<\/p>\n\n\n\n
That is the job of a Mutex<\/code>.<\/p>\n\n\n\n\n\n\n\n
2. sync.Mutex<\/code><\/h1>\n\n\n\n
What?<\/h2>\n\n\n\n
A mutex protects shared data so that only one goroutine changes it at a time.<\/p>\n\n\n\n
Put the mutex around the smallest section that accesses shared data<\/strong>.<\/p>\n\n\n\n\n\n\n\n
Complete Example<\/h1>\n\n\n\n
package main\n\nimport (\n\t\"fmt\"\n\t\"sync\"\n)\n\nfunc main() {\n\n\tvar wg sync.WaitGroup\n\tvar mu sync.Mutex\n\n\tcounter := 0\n\n\t\/\/ Start 1000 goroutines.\n\tfor i := 0; i < 1000; i++ {\n\n\t\twg.Add(1)\n\n\t\tgo func() {\n\n\t\t\tdefer wg.Done()\n\n\t\t\t\/\/ Only one goroutine can enter\n\t\t\t\/\/ this section at a time.\n\t\t\tmu.Lock()\n\n\t\t\tcounter++\n\n\t\t\tmu.Unlock()\n\t\t}()\n\t}\n\n\t\/\/ Wait for every goroutine.\n\twg.Wait()\n\n\tfmt.Println(\"Final counter:\", counter)\n}<\/code><\/pre>\n\n\n\n
Output:<\/p>\n\n\n\n
Final counter: 1000<\/code><\/pre>\n\n\n\n\n\n\n\n
Here we create a producer that could run forever.<\/p>\n\n\n\n
We give it a done<\/code> channel so it knows when to stop.<\/p>\n\n\n\n
package main\n\nimport (\n\t\"fmt\"\n\t\"sync\"\n)\n\nfunc producer(done <-chan struct{}, numbers chan<- int, wg *sync.WaitGroup) {\n\n\tdefer wg.Done()\n\tdefer close(numbers)\n\n\tnumber := 1\n\n\tfor {\n\n\t\tselect {\n\n\t\t\/\/ Try to send another number.\n\t\tcase numbers <- number:\n\n\t\t\tnumber++\n\n\t\t\/\/ Stop when main tells us\n\t\t\/\/ that the result is no longer needed.\n\t\tcase <-done:\n\n\t\t\tfmt.Println(\"Producer stopped\")\n\t\t\treturn\n\t\t}\n\t}\n}\n\nfunc main() {\n\n\tdone := make(chan struct{})\n\tnumbers := make(chan int)\n\n\tvar wg sync.WaitGroup\n\n\twg.Add(1)\n\n\tgo producer(done, numbers, &wg)\n\n\t\/\/ We only need 3 numbers.\n\tfor i := 0; i < 3; i++ {\n\n\t\tfmt.Println(\"Received:\", <-numbers)\n\t}\n\n\t\/\/ Tell producer:\n\t\/\/ we don't need any more values.\n\tclose(done)\n\n\t\/\/ Make sure producer actually exits.\n\twg.Wait()\n\n\tfmt.Println(\"Program finished cleanly\")\n}<\/code><\/pre>\n\n\n\n
package main\n\nimport (\n\t\"context\"\n\t\"fmt\"\n\t\"time\"\n)\n\nfunc worker(ctx context.Context) {\n\n\tfor {\n\n\t\tselect {\n\n\t\t\/\/ Simulate doing work repeatedly.\n\t\tcase <-time.After(500 * time.Millisecond):\n\n\t\t\tfmt.Println(\"Worker is working...\")\n\n\t\t\/\/ Stop when context is cancelled.\n\t\tcase <-ctx.Done():\n\n\t\t\tfmt.Println(\"Worker received cancellation\")\n\t\t\treturn\n\t\t}\n\t}\n}\n\nfunc main() {\n\n\t\/\/ Create a context that can be cancelled.\n\tctx, cancel := context.WithCancel(\n\t\tcontext.Background(),\n\t)\n\n\t\/\/ Start worker.\n\tgo worker(ctx)\n\n\t\/\/ Let it work for a short time.\n\ttime.Sleep(1600 * time.Millisecond)\n\n\tfmt.Println(\"Main: cancel the worker\")\n\n\t\/\/ Send cancellation signal.\n\tcancel()\n\n\t\/\/ Give worker time to print its final message.\n\ttime.Sleep(200 * time.Millisecond)\n\n\tfmt.Println(\"Main finished\")\n}<\/code><\/pre>\n\n\n\n
Possible output:<\/p>\n\n\n\n
Worker is working...\nWorker is working...\nWorker is working...\nMain: cancel the worker\nWorker received cancellation\nMain finished<\/code><\/pre>\n\n\n\n\n\n\n\n
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