Proper way to share state between custom value resolvers?

I have a situation where I can call/read SourceType.ExtractAsync() only once per instance but need to share the result across custom value resolvers.

I expected to use the ResolutionContext.Items for these types of tasks and be able to pass data/state from resolver to resolver. However, it's a read-only property.

That's why I've moved the reading part into a BeforeMap action and stored the result for reuse in a static property. However, I am unsure if this can lead to concurrency issues.

How should I exchange state between custom resolvers?

public class MessageProfiles : Profile
{
    public static List<string> SharedData = new();
    
    public MessageProfiles()
    {
        CreateMap<SourceType, DestinationType>()
            .BeforeMap((s, _) => SharedData = s.ExtractAsync().Result) // can only be read once!
            // ... 
            .ForMember(d => d.PropertyA, o => o.MapFrom<CustomResolverA>())
            .ForMember(d => d.PropertyB, o => o.MapFrom<CustomResolverB>())
            ;
    }
}

public class CustomResolverA : IValueResolver<SourceType, DestinationType, PropertyA>
{
    public PropertyA Resolve(SourceType source, DestinationType destination, PropertyA destMember, ResolutionContext context)
    {
        // Consume MessageProfiles.SharedData       
        // ... 
    }
}

public class CustomResolverB : IValueResolver<SourceType, DestinationType, PropertyB>
{
    public PropertyB Resolve(SourceType source, DestinationType destination, PropertyB, ResolutionContext context)
    {
        // Consume MessageProfiles.SharedData
        // ...
    }
}