rvest Error in function (type, msg, asError = TRUE) : Could not resolve host: google.com; Host not found

Question

I'm trying to use rvest package (downloaded from CRAN) to scrape certain contents from website but got an error:

library(rvest)    
html("http://google.com")

Here's the result:

Error in function (type, msg, asError = TRUE) : Could not resolve host: google.com; Host not found

I tried Sys.setenv(http_proxy = "webproxy:port") or set ./Renviron files and a few other tricks I found on stackoverflow but none works.