General aviation pilot reported flying within 300 feet of ground personnel on approach to a non-towered airport. They executed a go-around when they noticed the runway was marked closed; even though apparently no NOTAM had been published.

Narrative

We were doing a VFR flight for pleasure on Day 0. Our route took us from ZZZ - WLD - ZZZ1 - ZZZ. A full brief was done prior to departure including a review of NOTAMS at all airports. The only runway NOTAM in effect at WLD when we briefed was RWY35 PAPI out of service. We take off and are en route and pick up weather and descend on a straight in visual (no traffic in pattern observed or heard) to WLD RWY17. At approximately 500 feet AGL; we (pilot and passenger in copilot seat) notice what looks to be traffic holding short of RWY17. We note it and continue approach. At approximately 300 feet AGL; we notice workers on the runway and that it was a work truck at the hold short line. We immediately configure for a go around and offset the runway as to not overfly workers. I believe that the closure distance was <300 feet between us and workers. We continue our climb and fly a pattern and notice what looks to be a faint fabric/tarp 'X' laid out in the grass of the threshold without much color contrast to the ground.As we proceed to ZZZ1; I call Wichita TRACON and query if there was an active runway NOTAM closure that published at WLD while en route. They say no active runway closures were in force. I reported what I visually saw and they took the report. The rest of the flight was done without conflicts. Upon landing; we see a NOTAM published at XA:49 local time showing a runway closure. Take aways are to always practice see and avoid and overfly the runway if unsure of potentially dangerous conditions regardless of if NOTAM's are published. Also recommend that the airport manager ensure NOTAMS are published and that runway workers wear high visibility clothing so as not to blend into airport environment. Other recommendation is that higher contrast materials are used for the closure 'X' and that it is placed on the runway surface where pilots are typically focused.