Error self signed certificate in certificate chain

Erro in ionic start .
Error: self signed certificate in certificate chain
at TLSSocket. (_tls_wrap.js:1105:38)
at emitNone (events.js:106:13)
at TLSSocket.emit (events.js:208:7)
at TLSSocket._finishInit (_tls_wrap.js:639:8)
at TLSWrap.ssl.onhandshakedone (_tls_wrap.js:469:38)

my versions
node version : v8.11.2
npm version ; 6.1.0
cordova version : 8.0.0