Add lint checks: gofmt, goimports, golint

- gofmt - Gofmt checks whether code was gofmt-ed. By default this tool runs
  with -s option to check for code simplification
- goimports - Goimports does everything that gofmt does. Additionally it checks
  unused imports
- golint - Golint differs from gofmt. Gofmt reformats Go source code, whereas
  golint prints out style mistakes
    - checks the uncommented exported functions & types

Update the code to fix the lint checks.

common/account.go

@@ -13,6 +13,7 @@ import (
 )
 
 const (
+	// NLEAFELEMS is the number of elements for a leaf
 	NLEAFELEMS = 4
 	// maxNonceValue is the maximum value that the Account.Nonce can have (40 bits: maxNonceValue=2**40-1)
 	maxNonceValue = 0xffffffffff

common/exittree.go

@@ -6,6 +6,7 @@ import (
 	"github.com/iden3/go-merkletree"
 )
 
+// ExitInfo represents the ExitTree Leaf data
 type ExitInfo struct {
 	AccountIdx  Idx
 	MerkleProof *merkletree.CircomVerifierProof

common/fee.go

@@ -4,8 +4,9 @@ package common
 // to incentivaise the materialization of it
 type Fee float64
 
-// RecommendedFee is the recommended fee to pay in USD per transaction set by the coordinator
-// according to the tx type (if the tx requires to create an account and register, only register or he account already esists)
+// RecommendedFee is the recommended fee to pay in USD per transaction set by
+// the coordinator according to the tx type (if the tx requires to create an
+// account and register, only register or he account already esists)
 type RecommendedFee struct {
 	ExistingAccount           float64
 	CreatesAccount            float64
@@ -15,7 +16,9 @@ type RecommendedFee struct {
 // FeeSelector is used to select a percentage from the FeePlan.
 type FeeSelector uint8
 
+// MAXFEEPLAN is the maximum value of the FeePlan
 const MAXFEEPLAN = 256
 
-// FeePlan represents the fee model, a position in the array indicates the percentage of tokens paid in concept of fee for a transaction
+// FeePlan represents the fee model, a position in the array indicates the
+// percentage of tokens paid in concept of fee for a transaction
 var FeePlan = [MAXFEEPLAN]float64{}

common/l1tx.go

@@ -25,6 +25,7 @@ type L1Tx struct {
 	Type            TxType             `meddler:"tx_type"`
 }
 
+// Tx returns a *Tx from the L1Tx
 func (tx *L1Tx) Tx() *Tx {
 	return &Tx{
 		TxID:    tx.TxID,

common/l2tx.go

@@ -18,6 +18,7 @@ type L2Tx struct {
 	Type     TxType      `meddler:"tx_type"`
 }
 
+// Tx returns a *Tx from the L2Tx
 func (tx *L2Tx) Tx() *Tx {
 	return &Tx{
 		TxID:    tx.TxID,

common/pooll2tx.go

@@ -172,6 +172,7 @@ func (tx *PoolL2Tx) VerifySignature(pk *babyjub.PublicKey) bool {
 	return pk.VerifyPoseidon(h, tx.Signature)
 }
 
+// L2Tx returns a *L2Tx from the PoolL2Tx
 func (tx *PoolL2Tx) L2Tx() *L2Tx {
 	return &L2Tx{
 		TxID:     tx.TxID,
@@ -185,6 +186,7 @@ func (tx *PoolL2Tx) L2Tx() *L2Tx {
 	}
 }
 
+// Tx returns a *Tx from the PoolL2Tx
 func (tx *PoolL2Tx) Tx() *Tx {
 	return &Tx{
 		TxID:    tx.TxID,
@@ -197,6 +199,7 @@ func (tx *PoolL2Tx) Tx() *Tx {
 	}
 }
 
+// PoolL2TxsToL2Txs returns an array of []*L2Tx from an array of []*PoolL2Tx
 func PoolL2TxsToL2Txs(txs []*PoolL2Tx) []*L2Tx {
 	var r []*L2Tx
 	for _, tx := range txs {

common/scvars.go

@@ -6,6 +6,7 @@ import (
 	eth "github.com/ethereum/go-ethereum/common"
 )
 
+// RollupVars contain the Rollup smart contract variables
 type RollupVars struct {
 	EthBlockNum    uint64
 	ForgeL1Timeout *big.Int
@@ -15,6 +16,7 @@ type RollupVars struct {
 	Governance     eth.Address
 }
 
+// AuctionVars contain the Auction smart contract variables
 type AuctionVars struct {
 	EthBlockNum       uint64
 	SlotDeadline      uint
@@ -28,8 +30,10 @@ type AuctionVars struct {
 	AllocationRatio   AllocationRatio
 }
 
+// MinBidSlots TODO
 type MinBidSlots [6]uint
 
+// AllocationRatio TODO
 type AllocationRatio struct {
 	Donation uint
 	Burn     uint

common/zk.go

@@ -4,6 +4,8 @@ import (
 	"math/big"
 )
 
+// ZKInputs represents the inputs that will be used to generate the zkSNARK
+// proof
 type ZKInputs struct {
 	InitialIdx    uint64
 	OldStRoot     Hash
@@ -19,7 +21,7 @@ type ZKInputs struct {
 	TxData        []*big.Int
 
 	FromIdx     []uint64
-	ToIdX       []uint64
+	ToIdX       []uint64 //nolint:golint
 	ToAx        []*big.Int
 	ToAy        []*big.Int
 	ToEthAddr   []*big.Int
@@ -55,10 +57,7 @@ type ZKInputs struct {
 	OldValue2 []*big.Int
 }
 
+// CallDataForge TBD
 type CallDataForge struct {
 	// TBD
 }
-
-type ExitTreeLeaf struct {
-	// TBD
-}