### Installing go-eth2-client using go get

Source: https://github.com/attestantio/go-eth2-client/blob/master/README.md

This command installs the go-eth2-client library using the go get command. It fetches the module and its dependencies, making it available for use in Go projects.

```Shell
go get github.com/attestantio/go-eth2-client
```

--------------------------------

### Accessing a Beacon Node with go-eth2-client

Source: https://github.com/attestantio/go-eth2-client/blob/master/README.md

This example demonstrates how to connect to a beacon node, retrieve genesis information, and properly close the client connection. It showcases the use of the http package for creating a client, setting options like address and log level, and handling potential API errors.

```Go
package main

import (
	"context"
	"fmt"
	
	eth2client "github.com/attestantio/go-eth2-client"
	"github.com/attestantio/go-eth2-client/api"
	"github.com/attestantio/go-eth2-client/http"
	"github.com/rs/zerolog"
)

func main() {
	// Provide a cancellable context to the creation function.
	ctx, cancel := context.WithCancel(context.Background())
	client, err := http.New(ctx,
		// WithAddress supplies the address of the beacon node, as a URL.
		http.WithAddress("http://localhost:5052/"),
		// LogLevel supplies the level of logging to carry out.
		http.WithLogLevel(zerolog.WarnLevel),
	)
	if err != nil {
		panic(err)
	}
	
	fmt.Printf("Connected to %s\n", client.Name())
	
	// Client functions have their own interfaces.  Not all functions are
	// supported by all clients, so checks should be made for each function when
	// casting the service to the relevant interface.
	if provider, isProvider := client.(eth2client.GenesisProvider); isProvider {
		genesisResponse, err := provider.Genesis(ctx, &api.GenesisOpts{})
		if err != nil {
			// Errors may be API errors, in which case they will have more detail
			// about the failure.
			var apiErr *api.Error
			if errors.As(err, &apiErr) {
				switch apiErr.StatusCode {
				  case 404:
					panic("genesis not found")
				  case 503:
					panic("node is syncing")
				}
			}
			panic(err)
		}
		fmt.Printf("Genesis time is %v\n", genesisResponse.Data.GenesisTime)
	}

	// You can also access the struct directly if required.
	httpClient := client.(*http.Service)
	genesisResponse, err := httpClient.Genesis(ctx, &api.GenesisOpts{})
	if err != nil {
		panic(err)
	}
	fmt.Printf("Genesis validators root is %s\n", genesisResponse.Data.GenesisValidatorsRoot)

	// Cancelling the context passed to New() frees up resources held by the
	// client, closes connections, clears handlers, etc.
	cancel()
}
```

--------------------------------

### Fetching validators with new API style in Go

Source: https://github.com/attestantio/go-eth2-client/blob/master/docs/0.19.0-changes.md

This code snippet demonstrates the new way of fetching validators using the go-eth2-client, which involves passing parameters within a struct. This approach improves clarity and maintainability as the API evolves.

```go
validatorsProvider.Validators(ctx, &api.ValidatorsOpts{
  State: "head",
})
```

--------------------------------

### Fetching validators with old API style in Go

Source: https://github.com/attestantio/go-eth2-client/blob/master/docs/0.19.0-changes.md

This code snippet demonstrates the old way of fetching validators using the go-eth2-client, which involves passing parameters directly, including nil values. This approach can be unclear and difficult to maintain as the API evolves.

```go
validatorsProvider.Validators(ctx, "head", nil)
```

--------------------------------

### Handling errors with old API style in Go

Source: https://github.com/attestantio/go-eth2-client/blob/master/docs/0.19.0-changes.md

This code snippet demonstrates the old way of handling errors in the go-eth2-client, which involves checking for both a nil error and a nil result. This approach can be cumbersome and error-prone.

```go
block, err := beaconBlockProvider.SignedBeaconBlock(ctx, "999999999999")
if err != nil {
  panic(err)
}
if block == nil {
  panic("no block for this slot")
}
...
```

--------------------------------

### Handling errors with new API style in Go

Source: https://github.com/attestantio/go-eth2-client/blob/master/docs/0.19.0-changes.md

This code snippet demonstrates the new way of handling errors in the go-eth2-client, which involves checking for an error and then inspecting the error type. This approach provides better control of both successful and failed calls.

```go
response, err := beaconBlockProvider.SignedBeaconBlock(ctx, &api.SignedBeaconBlockOpts{
  Block: "999999999999",
})
if err != nil {
  var apiErr *api.Error
  if errors.As(err, &apiErr) {
    switch apiErr.StatusCode {
      case 404:
        // No block found.
      case 503:
        // Node is syncing.
    }
  }
  panic(err)
}
// At this point response will definitely not be nil.
...
```

--------------------------------

### Accessing metadata from response in Go

Source: https://github.com/attestantio/go-eth2-client/blob/master/docs/0.19.0-changes.md

This code snippet demonstrates how to access metadata from the response struct in the go-eth2-client. The metadata provides additional information about the response, such as whether a block is finalized.

```go
response, _ := beaconBlockProvider.SignedBeaconBlock(ctx, &api.SignedBeaconBlockOpts{
  Block: "123",
})

finalized, exists := response.Metadata[metadata.Finalized]
if exists {
  fmt.Printf("Is block finalized? %b\n",finalized)
}
```

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