Tuve este script de ayuda de prueba:

#!/usr/bin/env bash

export GOPATH="$PWD"
export GOCACHE="off" 

if [[ -z "$2" ]]; then
     go test -test.v "$1" 
else
     go test -test.v -run "$1"  "$2"
fi

en mi infinita curiosidad lo cambio a:

export GOCACHE="on"

y ahora tengo un montón de archivos en el directorio / on, se ve así:

rm 'on/f5/f545eea03c3b3918eb9ea8da640e4096bb88e737da8fe79b982282e391034a00-d'
rm 'on/f5/f5f8e6ba734b39e6e3994bd38ae138ee5f1c934fb31aa3d67b6ebab51e064550-d'
rm 'on/f7/f77ddf07d9322f6fc37a8ccd8a3b1e204df20269d046d9f26e514ce8ee71dd24-a'
rm 'on/f9/f95e42f33f46590cc13a52c8c5ced78ee10b1d6223116b96e5048bbfca45a8fa-a'
rm 'on/f9/f960e1bdd90bdbedd9c1b6a4f84034b695366008fe9572f8eade4d6091ab7783-a'
rm 'on/f9/f983bb0548444122f704c06b85bfc940edea3ad6674c8bed4b259d3682e61ed6-a'
rm 'on/fa/fa0f06fb98f8e24e2896e173fa5ffafe741f388ecbc0ab05980bc6d7e582822e-a'
rm 'on/fa/fa21e4bcc0150a1df51f1c0342c16a12a1bbf3fc6266258794e8c4bed7366bd7-d'
rm 'on/fa/fac556023783b822b6b37ae37bf02932456e965ad1b37f4e45419c9779eb648e-a'
rm 'on/fb/fb1df4e560bc5701575401f7a3f12d29545b2ff1b931852f45f5e79ff798ab0e-a'
rm 'on/fb/fb32adee7638f775a9161a321db4fc76419e6370795c0d83d51a9edc116d3c65-a'
rm 'on/fb/fbd3f0a0b1bcb06b94a210547b346183455be303d482240b6e3b775ad91141c1-d'
rm 'on/fb/fbf683cd1314637c28aaf4fb65205d990c459938c32673d6492b0a046c5a2483-d'
rm 'on/fc/fc40abd0343f9a80c5b3dab549574858d22f9d70262ed2d3a847fdb54e3e303e-d'
rm 'on/fc/fc55620605eb3828cb262ebff9a1e314f65646349b01e6d7b2fb71b68a24b067-a'
rm 'on/fc/fc6ca27ea05682c412053e174d21b2736ede872a69331fb58fb740

¿Alguien sabe de qué se trata?