Declaring all the possible TokenType

token/token.go

@@ -6,3 +6,25 @@ type Token struct {
 	Type    TokenType
 	Literal string
 }
+
+const (
+	ILLEGAL = "ILLEGAL"
+	EOF     = "EOF"
+
+	IDENT = "IDENT"
+	INT   = "INT"
+
+	ASSIGN = "="
+	PLUS   = "+"
+
+	COMMA     = ","
+	SEMICOLON = ";"
+
+	LPAREN = "LPAREN"
+	RPAREN = "RPAREN"
+	LBRACE = "LBRACE"
+	RBRACE = "RBRACE"
+
+	FUNCTION = "FUNCTION"
+	LET      = "LET"
+)