How to Pass Multiple Key-Value Pairs to a Context in Go?

context.WithValue: Passing Multiple Key-Value Pairs

In Go's context package, you can add key-value pairs to a context using the WithValue() function, which returns a new context with the added pair. However, what if you need to pass multiple key-value pairs to a context?

Option 1: Call WithValue() Multiple Times

You can call WithValue() multiple times, passing the new context as the first argument each time:

import (
    "context"
)

func main() {
    // Create a background context.
    ctx := context.Background()

    // Add key-value pairs one by one.
    ctx = context.WithValue(ctx, "key1", "value1")
    ctx = context.WithValue(ctx, "key2", "value2")
}

Option 2: Use a Data Structure

If you need to add multiple key-value pairs, it can be more efficient to use a single data structure to hold them. You can then add the whole data structure to the context using WithValue():

type MyStruct struct {
    Key1 string
    Key2 string
}

func main() {
    // Create a context.
    ctx := context.Background()

    // Create a data structure.
    data := MyStruct{
        Key1: "value1",
        Key2: "value2",
    }

    // Add the data structure to the context.
    ctx = context.WithValue(ctx, "mydata", data)
}

Option 3: Hybrid Solution

You can also use a hybrid approach, where you create a wrapper struct that holds a map of key-value pairs. You can then add the wrapper struct to the context:

type MyWrapper struct {
    m map[string]string
}

func (w *MyWrapper) Get(key string) string {
    return w.m[key]
}

func main() {
    // Create a context.
    ctx := context.Background()

    // Create a wrapper struct.
    wrapper := MyWrapper{
        m: map[string]string{
            "key1": "value1",
            "key2": "value2",
        },
    }

    // Add the wrapper struct to the context.
    ctx = context.WithValue(ctx, "mywrapper", wrapper)
}

Conclusion

The approach to use will depend on the specific use case and performance requirements. If you need to add a small number of key-value pairs with minimal overhead, you can use Option 1. If performance is a concern, you may want to use Option 2 or Option 3.

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