Loading required package: shiny
Loading required package: methods

Listening on http://127.0.0.1:8765
Warning: Error in badservercall: server boom
Stack trace (innermost first):
    41: badservercall [${PWD}/stacktrace5/server.R#4]
    40: server [${PWD}/stacktrace5/server.R#9]
     1: shiny::runApp [${SHINY}/R/server.R#685]
Error in badservercall() : server boom
NULL