Expose blockchain via RESTful API using Fiber or Gin

[devduart]

Summary

Create a REST API to interact with the blockchain over HTTP using either Fiber or Gin.

Tasks

• Setup HTTP server (Fiber or Gin)
• Endpoints:
  • GET /blocks – list all blocks
  • POST /mine – mine a new block with JSON data
  • GET /block/:hash – get block by hash
• Return data in JSON format
• Validate request body and handle errors

Bonus

• Include difficulty in JSON response
• Add timestamp to responses