Why is an additional block of curly braces used in the function?

An additional block of curly braces inside a function creates a new scope. This is useful in the following cases:

1. Temporary memory allocation: Variables declared inside such a block exist only within this block. After exiting it, the memory allocated for these variables can be freed by the garbage collector. This helps manage resources, especially in long loops or when working with many temporary objects.

   func processData(data []*int) {
       for _, item := range data {
           { // Start of a new scope
               tempVar := *item * 2 // tempVar is only visible here
               if tempVar > 100 {
                   // do something
               }
           } // tempVar no longer exists
           // tempVar is inaccessible here
       }
       // tempVar is inaccessible here
   }
   

2. Managing defer: Instructions placed inside the block will be executed exactly when exiting this block, not the entire function. This allows controlling the timing of deferred operations, such as closing files or unlocking mutexes, before the whole function finishes.

   func readFile(filename string) ([]byte, error) {
       f, err := os.Open(filename)
       if err != nil {
           return nil, err
       }
       // defer f.Close() // This will close at the end of the function
   
       { // Start of a new scope
           defer f.Close() // This will close when exiting this block
           // Reading from f
           data, readErr := ioutil.ReadAll(f)
           if readErr != nil {
               return nil, readErr
           }
           return data, nil
       } // f.Close() will be called here
   
       // f is already closed
   }
   

3. Improving readability: In some rare cases, explicitly isolating a code section in a block can improve readability by grouping related operations and demonstrating their limited scope. However, overusing this can make the code less understandable.

Overall, the main goal is to create a limited scope for managing variable lifetimes and executing deferred operations (defer).