What is the usage of Context in the Go language?

In the Go language, Context is a mechanism used to control concurrency. It allows for passing data between multiple goroutines, cancelling goroutine execution, and setting deadlines.

Common uses of Context include the following aspects:

1. Passing data: Using Context, it is possible to transfer context-related data between goroutines. For example, request metadata (such as user ID, access token, etc.) can be stored in Context and then passed to relevant goroutines throughout the entire request handling process.
2. Control concurrency: By using the cancellation mechanism of Context, it is possible to cancel the execution of a group of related goroutines. When a Context is cancelled, the goroutines associated with it can perform appropriate cleanup work and exit based on the cancellation signal.
3. Set deadline: By using Context, you can set a deadline for a goroutine. When the deadline is exceeded, you can trigger corresponding actions, such as cancelling the execution of the goroutine or returning a timeout error.
4. Monitoring and tracing: Using Context, monitoring and tracing information can be passed throughout the entire request processing chain. For example, request handling times, logs, metrics, and other related information can be recorded in Context, making it easier to conduct performance analysis and troubleshoot issues.

Context is a data structure based on a tree-like structure, that can be created and manipulated using functions like WithCancel, WithTimeout, and WithValue. When using Context, it is important to follow best practices such as canceling the Context promptly and avoiding storing a large amount of data in the Context to ensure maintainability and performance of the code.