check null result

Author: lizekun

geth.go

@@ -1,6 +1,7 @@
 package etherscan
 
 import (
+	"math/big"
 	"strconv"
 )
 
@@ -13,3 +14,9 @@ func (c *Client) GetBlockByNumber(blockNum int64) (block Block, err error) {
 	err = c.call("proxy", "eth_getBlockByNumber", param, &block)
 	return
 }
+
+func (c *Client) GasPrice() (price *big.Int, err error) {
+	param := M{}
+	err = c.call("proxy", "eth_gasPrice", param, price)
+	return
+}