Allow hyphens in identifiers

src/lexer.rs

     static ref MATCHERS: Vec<Matcher> = vec![
         Matcher::new(r#""(.*)""#, TokenType::String),
         Matcher::new(r#"(SELECT|FROM)"#, TokenType::Keyword),
-        Matcher::new(r#"[a-z][a-zA-Z_]*"#, TokenType::Identfiier),
+        Matcher::new(r#"[a-z][a-zA-Z_\-]*"#, TokenType::Identfiier),
         Matcher::new(r#"[0-9]+"#, TokenType::Number),
         Matcher::new(r#"\*"#, TokenType::Star),
     ];
         )
     }
 
+    #[test]
+    fn it_allows_hyphens_in_identifiers() {
+        assert_eq!(
+            scan("abc-def").unwrap(),
+            vec![Token::new(TokenType::Identfiier, "abc-def")]
+        )
+    }
+
     #[test]
     fn it_scans_a_star() {
         assert_eq!(scan("*").unwrap(), vec![Token::new(TokenType::Star, "*")])