String from struct pointer - json

Question

As a student of Go I encountered this problem.
My ultimate goal of doing this is to convert *blockchain into a valid JSON string.
My structs are:
type Blockchain struct{
blocks []Block `json:"blocks"`
difficulty int `json:"difficulty"`
}
type Block struct{
index int `json:"index"`
timestamp string `json:"timestamp"`
data string `json:"data"`
previousHash string `json:"previousHash"`
hash string `json:"hash"`
nonce int `json:"nonce"`
}
I have the following code:
var s = fmt.Sprintf("%#v", *blockchain)
print(s)
Which gives me the following:
main.Blockchain{blocks:[]main.Block{main.Block{index:1, timestamp:"2019-04-06 12:50:54", data:"Genesis block", previousHash:"", hash:"eca16d7bdd20a91f471fc3231fa5de7d892fb540789673d64f29a7b93719b74b", nonce:0}, main.Block{index:2, timestamp:"2019-04-06 12:50:54", data:"d.duck", previousHash:"eca16d7bdd20a91f471fc3231fa5de7d892fb540789673d64f29a7b93719b74b", hash:"2096ccfa6fdd8305f0e31c2e6858173a21764be4c8e1d3d50c9c31193bf06a2a", nonce:0}, main.Block{index:3, timestamp:"2019-04-06 12:50:54", data:"dumbo", previousHash:"2096ccfa6fdd8305f0e31c2e6858173a21764be4c8e1d3d50c9c31193bf06a2a", hash:"d76d4a002c6dde01009e3122aa1ccfb455e1d453ac83e2a0eb123c6080943cdb", nonce:0}}, difficulty:4}
Obviously invalid JSON.
Any suggestions?
I also tried the following:
var json, err = json.Marshal(*blockchain)
if err != nil{
panic(err.Error())
}
var s = fmt.Sprintf("%#v", json)
print(s)
It gave me the following:
[]byte{0x7b, 0x7d}

Answer 1

The fields on structs need to be exported (start with capital letter). This is required because JSON marshalling uses reflection, and that requires the field to be exported (to be visible).
Also json.Marshal first return value is the JSON.
package main
import (
"encoding/json"
"fmt"
"log"
)
type Blockchain struct {
Blocks []Block `json:"blocks"`
Difficulty int `json:"difficulty"`
}
type Block struct {
Index int `json:"index"`
Timestamp string `json:"timestamp"`
Data string `json:"data"`
PreviousHash string `json:"previousHash"`
Hash string `json:"hash"`
Nonce int `json:"nonce"`
}
func main() {
bc := &Blockchain{
Blocks: []Block{
Block{},
},
Difficulty: 1,
}
v, err := json.Marshal(bc)
if err != nil {
log.Fatal(err)
}
fmt.Println(string(v))
}
This prints:
{"blocks":[{"index":0,"timestamp":"","data":"","previousHash":"","hash":"","nonce":0}],"difficulty":1}