code: func (c *Cursor) seek(seek []byte) (key []byte, value []byte, flags uint32) {
  	_assert(c.bucket.tx.db != nil, "tx closed")
  
  	// Start from root page/node and traverse to correct page.
  	c.stack = c.stack[:0]
  	c.search(seek, c.bucket.root)
  	ref := &c.stack[len(c.stack)-1]
  
  	// If the cursor is pointing to the end of page/node then return nil.
  	if ref.index >= ref.count() {
  		return nil, nil, 0
  	}
  
  	// If this is a bucket then return a nil value.
  	return c.keyValue()
  }
docs: // seek moves the cursor to a given key and returns it.
  // If the key does not exist then the next key is used.