Implement first iteration of node

The coordinator implementation has been refactored to allow all the goroutines
to be handled from the node.

config/config.go

@@ -0,0 +1,101 @@
+package config
+
+import (
+	"fmt"
+	"io/ioutil"
+	"time"
+
+	"github.com/BurntSushi/toml"
+	ethCommon "github.com/ethereum/go-ethereum/common"
+	"gopkg.in/go-playground/validator.v9"
+)
+
+// Duration is a wrapper type that parses time duration from text.
+type Duration struct {
+	time.Duration
+}
+
+// UnmarshalText unmarshalls time duration from text.
+func (d *Duration) UnmarshalText(data []byte) error {
+	duration, err := time.ParseDuration(string(data))
+	if err != nil {
+		return err
+	}
+	d.Duration = duration
+	return nil
+}
+
+// Coordinator is the coordinator specific configuration.
+type Coordinator struct {
+	ForgerAddress     ethCommon.Address `validate:"required"`
+	ForgeLoopInterval Duration          `validate:"required"`
+}
+
+// Node is the hermez node configuration.
+type Node struct {
+	StateDB struct {
+		Path string
+	} `validate:"required"`
+	PostgreSQL struct {
+		Port     int    `validate:"required"`
+		Host     string `validate:"required"`
+		User     string `validate:"required"`
+		Password string `validate:"required"`
+	} `validate:"required"`
+	L2DB struct {
+		Name         string   `validate:"required"`
+		SafetyPeriod uint16   `validate:"required"`
+		MaxTxs       uint32   `validate:"required"`
+		TTL          Duration `validate:"required"`
+	} `validate:"required"`
+	HistoryDB struct {
+		Name string `validate:"required"`
+	} `validate:"required"`
+	Web3 struct {
+		URL string `validate:"required"`
+	} `validate:"required"`
+	TxSelector struct {
+		Path string `validate:"required"`
+	} `validate:"required"`
+	BatchBuilder struct {
+		Path string `validate:"required"`
+	} `validate:"required"`
+	Synchronizer struct {
+		SyncLoopInterval Duration `validate:"required"`
+	} `validate:"required"`
+}
+
+// Load loads a generic config.
+func Load(path string, cfg interface{}) error {
+	bs, err := ioutil.ReadFile(path) //nolint:gosec
+	if err != nil {
+		return err
+	}
+	cfgToml := string(bs)
+	if _, err := toml.Decode(cfgToml, cfg); err != nil {
+		return err
+	}
+	validate := validator.New()
+	if err := validate.Struct(cfg); err != nil {
+		return fmt.Errorf("error validating configuration file: %w", err)
+	}
+	return nil
+}
+
+// LoadCoordinator loads the Coordinator configuration from path.
+func LoadCoordinator(path string) (*Coordinator, error) {
+	var cfg Coordinator
+	if err := Load(path, &cfg); err != nil {
+		return nil, fmt.Errorf("error loading coordinator configuration file: %w", err)
+	}
+	return &cfg, nil
+}
+
+// LoadNode loads the Node configuration from path.
+func LoadNode(path string) (*Node, error) {
+	var cfg Node
+	if err := Load(path, &cfg); err != nil {
+		return nil, fmt.Errorf("error loading node configuration file: %w", err)
+	}
+	return &cfg, nil
+}