Adding to @Reimeus answer,
Make sure to keep MyController class and BackendApplication class within main package i.e, com.iz.backend.
 |-src/main/java
    |--com.iz.backend 
       |--controllers
          |--MyController
       |--BackendApplication
Or, use basePackages:
@SpringBootApplication(scanBasePackages = {"com.iz.backend"}) 
5
solved @RequestMapping spring boot doesn’t function as expected