Issues with sending requests containing certain characters

[cal-anthropic]

Repro

package main

import (
	"context"
	"os"

	"github.com/anthropics/anthropic-sdk-go"
	"github.com/anthropics/anthropic-sdk-go/option"
)

func main() {
	client := anthropic.NewClient(
		option.WithAPIKey(os.Getenv("ANTHROPIC_API_KEY")),
	)
	message, err := client.Messages.New(context.TODO(), anthropic.MessageNewParams{
		Model:     anthropic.F(anthropic.ModelClaude3_5SonnetLatest),
		MaxTokens: anthropic.F(int64(1024)),
		Messages: anthropic.F([]anthropic.MessageParam{
			anthropic.NewUserMessage(anthropic.NewTextBlock("What is a quaternion?\x1b")),
		}),
	})
	if err != nil {
		panic(err.Error())
	}
	println(message.Content[0].Text)
}

Output:

POST "https://api.anthropic.com/v1/messages": 400 Bad Request {"type":"error","error":{"type":"invalid_request_error","message":"The request body is not valid JSON: invalid escaped character in string: line 1 column 75 (char 74)"}}